Combat-wise, it feels a bit much.

I recently started a druid. My first intent was to find a way to remain effective in combat despite depleted resources ; I found out that the druid hasn't much to offer, in that regard:

1. Ranged options (such as sling attacks, or produce flame) lack range and damage.
2. Melee options (such as shillelagh or thorn whip) lack damage in the long run.
3. AC is often on the low-end - unless your DM is generous on non-metal armor distribution, or you focus on dexterity.

It is indeed very frustrating, and encourages battlefield control over direct damage. Your homebrew subclass fixes all 3 issues, including strong blaster, healer and tank features: it would have been a no-brainer for me, and that's a warning for balance.

Bladesinger comparison

There are not that many full spellcasters with Extra Attack, and Bladesong looks very close to Heart of Fire. It may seem balanced... until you dig a little more:

\$\begin{array}{|c|c|c|} \hline \textbf{Ability} & \textbf{Bladesinger} & \textbf{Circle of flame}\\ \hline \text{max AC using mundane gear} & 23 & \textbf{25} \\ \text{Requirements:} & \textit{mage armor}\text{ spell} & \text{shield, class level 18} \\ & \text{high dexterity & intelligence} & \text{high dexterity or nonmetal half-plate} \\ \hline \text{max AC using magical items} & 25 & \textbf{31} \\ \text{Requirements:} & \textit{robe of the archmagi} & \text{+3 shield & armor, class level 18} \\ & \text{high Dexterity & Intelligence} & \text{high Dexterity or nonmetal half-plate} \\ \hline \text{Hit dice} & \text{d6} & \textbf{d8} \\ \hline \text{Damage control} & \text{reaction & spell slots-based} & \textbf{healing spells} \\ & \text{Damage reduction} & \textbf{reaction-based healing} \\ \hline \text{Concentration}& \text{+Intelligence modifier} & \text{better AC = fewer concentration checks} \\ \hline \end{array} \$

All in all, the Circle of the Flame druid vastly outperforms its cousin - and can even do so with little ASI investment, should you find a proper armor.

Circle of Land & Circle of Spores comparisons

The Circle of Spores, from Unearthed Arcana, is probably an attempt to offer wannabe-melee druids an alternate to the circle of the moon's combat forms. Let's include it here:

\$\begin{array}{|c|c|c|} \hline \textbf{Subclass features} & \textbf{Circle of the Flame} & \textbf{Circle of the Land} & \textbf{Circle of Spores} \\ \hline \text{level 2} & \textbf{$fire\ bolt$} & \text{one druid cantrip} & \textit{chill touch} \\ & \textbf{1-minute huge melee buff} & \text{Natural Recovery} & \text{10-min small melee buff} \\ & & & \text{reaction-based poison damage} \\ \hline \text{level 6} & \textbf{Extra Attack} & \text{ignoring difficult terrain} & \text{1-hp zombies} \\ \hline \text{level 10} & \textbf{+Wis mod to fire, concentration spells} & \text{various immunities} & \text{AoE spores} \\ & \textbf{fire resistance} & & \\ \hline \text{level 14} & \textbf{turn fire/lightning damage into healing} & \text{beasts & plants hesitate to attack} & \text{various immunities} \\ \hline \end{array} \$

It looks like the Circle of the Flame has the best features at each level: best cantrip to allow ranged combat, best melee-buff, extra attack is sick, enhancing concentration-based spells is unique... Even the last feature, that appears situational at first, becomes cheesy once you start to fuel it with your own AoE spells.

Suggestions

So, how do we fix this?

First, you can't aim for balance, and be a strong healer, blaster and tank at the same time. I removed the healing capabilities, as the tank part seemed your main concern, and the theme calls for improved fire damage.

Second, on the AC question: "no metal armor" and bounded accuracy make things difficult. If your DM rewards you with powerful nonmetal armors, he shouldn't allow big AC temporary bonuses in an homebrew class. The opposite is also true: if he allows big AC temporary bonuses... he should make sure you keep a lowly hide armor for your entire career. Hence the solution offered here - which seems the good way to reliably get good AC, without over-investing in dexterity or "forcing the hand" of your DM.

Here's the result:

Only You

When you choose the Circle of Flame at level 2, fire bolt and green-flame blade become druid cantrips for you. You learn an additional druid cantrip of your choice.

Leaves choices, and includes another fire-themed cantrip. Green-flame blade is mostly aimed at tier 2+ melee: extra attack was too much (especially if you intend to add Polearm Master), but this cantrip offers something comparable to the cleric's Divine Strike.

Heart of the Flame

At 2nd level, you gain the ability to awaken the primal spirits of flame. As a bonus action, you can expend a use of your Wild Shape feature to awaken your inner flame, rather than transforming into a beast form. While this feature is active, you gain the following benefits:

• You gain 3 temporary hit points per level you have in this class
• You shed bright light in a 30-foot radius and dim light for an additional 30 feet.
• You add your Wisdom modifier to concentration checks.

These benefits last for 10 minutes, or until you become unconscious.

Temporary HP is probably the way to go to add survivability to a druid: it matches what has been done for the Circle of Spores and Circle of the Moon. I removed the AC boost: if you insist on keeping it, you'll have to either keep it low (like +2), or remove the ability to use a shield - if you care about bounded accuracy, of course.

Purification through Fire

Starting at level 6, you gain resistance to fire damage. You also learn a purification ritual that allows you to prepare metal shields & armors, so that you can use them.

With your average 14-dex druid, it means up to +3 AC - and an easier access to magic armor in the long run. It is a game changer for most tables, where nonmetal armor is scarce - and can be balanced by making the ritual as simple or as complex as you wish (involving time, gold, crafting skills, a risk to destroy the item?).

Heat of Battle

Starting at level 10, once per turn, whenever one of your spells inflicts fire damage to a creature, you can add your Wisdom modifier to that damage.

Idea is to open that damage buff to more options (e.g fire bolt, green-flame blade) - while keeping it at a reasonable level (only one creature per turn).

Flaming Soul

Starting at level 14, you gain immunity to fire damage. You can also apply your heat of battle on a second damage roll, each turn.

Either affect both targets of green-flame blade, or use it on both flaming sphere and your cantrip of choice.

I'm absolutely not sure that this is well balanced:

• I feel Nature and/or Forge Domain clerics might feel cheated with this, as some of their core subclass features are included here, with few drawbacks
• having both a better AC and temporary HP, while keeping access to healing spells, means that you are tanking pretty hard
• Extra attack was too much - and this may also be. Green-flame blade + Heat of Battle + shillelagh makes a strong combination.
• Bonus to concentration might go out of control if you go for the War Caster / Resilient (Con) route. Replacing it with Con save proficiency or advantage on concentration checks may help avoid those shenanigans.

But I do think it is closer to "balanced", when compared with Land & Spores druids. Obviously, feel free to switch things around (access to metal armor as soon as level 2?) - and take or leave whatever fits best your idea.

This answer is going to come off as extremely negative. Unfortunately that is my best analysis of the class. So before I get into I want to say; I love the theme of what you were going for. A patron that could be a level 20 character from a previous campaign is great. I also don't want to discourage you from homebrewing stuff in general, this class has a lot of issues though and I felt it was necessary to point them out.

This is unbalanced and breaks the style of warlock patrons

This patron makes such a departure from the typical structure of a warlock patron that it is somewhat difficult to assess in balance terms. My gut says it is very over-powered and I will try to go through each feature to explain why. Note; this analysis is focused on comparing it to other patrons not the entire warlock class.

Expanded Spell List

A standard feature of warlock patrons that you have re-interpreted, both in good and bad ways. Overall your version is overpowered and needs to be fixed.

Spell List As Spells Known

The PHB patrons get access to 2 spells of each level from 1st to 5th. They are simply added to the spell list and do not add to spells known. The celestial and hexblade patrons from XGtE only get access to 1 spell of each level but they still do not count as known spells.

Expanding the spells known of the warlock is completely against the design of all other patrons. This part of the feature is completely broken and needs to be removed.

@illustro points out that as worded this does not add additional spells known but instead forces the warlock to learn those spells. If this is the case then this feature is actually extremely weak, far worse than any of the other patron spell list options.

Choice of spell list

The choice of three different lists based on the spellcasting class of the patron is a cool thematic choice. However all three lists contain spells that are already available to the base warlock. The warlock list is worse than useless, while major image from the wizard list and banishment from the sorcerer list are already available to warlocks.

I would like to see this feature remain but it needs work on the spells chosen. I would drop the warlock list and a add bard, and/or druid list instead.

Lesser Mystic Arcanum

Nope. This feature is entirely broken. At 9th level your warlock has an additional 5 spell slots per day above and beyond their typical 3 per short rest. Not all warlock spells benefit from up-casting and having them in lower level slots does not sufficiently reduce their power. Giving this many additional spells is way, way stronger than anything any of the other patrons give at this level or at any level.

There is no point even comparing this to the other patrons in detail. In summary it is very overpowered and needs to be removed entirely.

Strategic Spell

This one isn't too bad. Rogues and monks already have access to this feature. However it does go against the normal style of the warlock. Apart from the celestial patron every other patron grants a once per short rest ability not an always on feature. By not being limited to pact slots this feature works on cantrips and is therefore infinite.

To answer your follow up questions, removing Dash makes no real difference, Disengage and Dash are about equal. And no; you absolutely should not include Dodge. Dodge is way stronger than either of the others, there is a reason rogue's cunning action does not include it.

This feature is likely a little overpowered due to unlimited uses, but only when compared to the other warlock patrons. Overall this feature is not game-breaking given you should be at range anyway.

Eldritch Weave

At first this one seems ok, but it is likely overpowered. Gaining temporary hitpoints is very similar to the Celestial Resistance feature of that patron, though that one allows you to also protect other creatures.

The issue with this feature is the additional feature: "your concentration cannot be broken until you lose all of these temporary hit points". This is extremely strong. Spellcasters typically take entire feats (War Caster, Resilient (Con)) just to buff their concentration checks. Your feature is negating them entire for a minute.

Yes, this benefit ends early if you get hit enough. But, at a minimum of 20HP and increasing every level this will take a few rounds. Assuming you are concentrating on some disabling spell like hold person or similar it might be impossible for the enemy to deal enough damage to break this before your party takes out your target.

This feature is overpowered and should be changed.

Greater Mystic Arcanum

If the early version of this feature wasn't so utterly unbalanced this would almost be fine. However; it isn't, and neither is this. At will hex at 14th level, then suggestion at 18th level is very powerful.

In fact this feature is exactly eqivilent to the 18th level Spell Mastery feature of the wizard, barring some flexibility. No other patron gets a feature anything like this. Several only get a single once per long rest ability.

At will casting of leveled spells is normally restricted to Eldritch Invocations. Allowing it in addition to those completely breaks the style and design of the Warlock. This is utterly unbalanced and needs to be removed.

Conclusion

Scrap the whole thing. The features are almost all overpowered and don't suit the style of the Warlock at all. Any one of the features (bar Strategic Spell) would be enough to make this class overpowered. Added together this is completely busted.

You are adding flexibility by increasing spells known with your 1st level features, and you are increasing overall power level by giving out way more spell slots. This Warlock is so much better than the others there is almost no reason to look at them unless you want to be a melee fighter.

Back to the drawing board for this one.