This is almost balanced and ready for playtesting
In balance terms I think you have got this about as balanced as you can without playtesting, except for the 10th level feature. Fixing that then playtesting should be your next step. I expect you will find that some features are overpowered but the lack of slot recovery and the few underpowered feature balance it out overall. As usual I will still go through each feature and give some feedback.
Level 2
Bonus cantrip is good, you are giving access to something druids don't normally get so that makes up for that lack of choice compared to the Circle of the Land. I'm not fussed about the theme of Life/Death from Chaos but that is clearly what you are going for so that's alright. I would grant a more damaging cantrip like firebolt or acid splash to better suit the offensive theme.
1/20 chance of a free Wild Shape is cool and on theme. Though without the forms of Circle of the Moon and no casting in Wild Shape it isn't super useful. This feature is likely slightly underpowered compared to Natural Recovery but not too bad.
Circle Spells
- Crown of Madness: Yes! Totally on theme, a perfect choice
- Shatter: A good AoE attack spell that suits the theme. Good choice.
- Bestow Curse: Pretty good debuff spells that suits the theme. Not bad.
- Vampiric Touch: This is a little more death than Chaos to me. But I get that you want the healing from death type thing. Not a terrible spell choice.
- Death Ward: Not sure about the chaos part of this spell. It feels more like preventing chaos than causing it.
- Greater Invisibility: Not a bad option, it doesn't not suit the theme. Though you do have a lot of concentration spells to compete with it.
- Dawn: Was good before, still good now.
- Destructive Wave: Destructive chaos, basically built of this class. Good choice.
Most of your spell choices are pretty good. Some alternate suggestion for 7th level are: banishment, Evard's black tentacles, confusion, phantasmal killer and vitriolic sphere.
Also the suggestion by Rorp to give chaos bolt is awesome from a theme point of view. Unfortunately it is level 1 and doesn't suit the circle spell progression. I would consider finding a way to fit it in. Maybe instead of the free cantrip at 2nd level you give a 1/rest casting of Chaos Bolt.
Level 6
This is more balanced recharging only on a long rest. I'm not sold on the theme of it but it isn't an issue.
Level 10
Compared to the Circle of the Land this feature is way better. They get immunity to poison and disease, and charm and frightened from fey or elemental. Circle of the Moon get Elemental Wild Shape, Circle of the Shepherd get healing aura for summoned creatures, Circle of Dreams get a limited use teleport. You give advantage on all spell saves, all the time, with no restrictions.
As you say Yuan-ti Pureblood get this as a racial trait from 1st level. While this is support that the feature is not unbalance in general, it is still much stronger than anything the other circles get at this level.
The cantrip as a reaction thing is fine. It might be a little strong if you take my earlier suggestion to give a high damage cantrip but still not a huge deal. Combined with the other benefit is definitely pushes this into overpowered though. I would add some restriction to the magic resistance and cut this part for playtesting.
Level 14
Casting two spells in a turn 1/6 of the time could be really strong. However you will burn spells very quickly. I would limit it to not work on cantrips as that would just make it free damage with no cost. If this proves too strong during playtesting you could consider limiting this action to one weapon attack, Dash, Disengage, Hide, or Use an Object; the same as the action granted by the haste spell.
I love the theme of this ability and think you should stick with it, but be prepared to modify it if it proves too strong.
Why I think spell recovery is important
You say you want this class to be a primary caster druid. Every other primary offensive caster (Circle of the Land druid, wizard, sorcerer, warlock) have a way of regaining some spells on a short rest (sorcerer via sorcery points). Bard and cleric regain other magic-like abilities (Bardic Inspiration and Channel Divinity receptively) on a short rest. Circle of the Moon druids get their main offense (Wild Shape) back on short rests.
Most of these classes also have better offensive cantrips than the druid and don't rely so heavily on spell slots for damage. You are relying on spell slots and not giving a way to recover them. This puts you at a significant disadvantage compared to every other primary caster. That is why I have suggested it multiple times.
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.
Best Answer
Surprisingly, this is slightly underpowered, though quite similar to the Lore Mastery subclass, which I will compare it to. Compared to the PHB classes only, however, it is balanced.
Borrowing Threads: This is far worse than Lore Mastery, which can change the damage types of any spell at will, and gets expertise in 4 skills, can use INT for initiative, and can change a saving throw, all at level 2.
Reweaving Techniques: You get access to counterspell at level 5, so it is balanced to give a once per long rest improved version of it. Similar to rogue spell thief, but more powerful as you are a full caster, not a third caster.
Correct Misthreadings: This is actually fairly weak, as you still use another spell slot, so all you are saving is an action. Compare this to the Lore Master, who by this time can prepare any spell they know as a bonus action, hit enemies a mile away, or increase their DC by 2. I would rather use my familiar or my allies to impose disadvantage on my enemies saves then spend another spellslot with another risk of failure.
Pieces of the Tapestry: This is on par with the Lore Mastery's ability. They get to cast any spell from any spell list once per long rest. You only get that for cantrips, but you can do it thrice per long rest, and can also get magic resistance or a free 6th level spell.
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