Are there actual rules for the results of dragon crossbreeding

The only thing that is directly answered by the rules is the cost.

PHB pg 112:

Wealth Other than Coins:
Trade Goods Table
1 lb of Tobacco costs 5 sp.

As far as effects, they don't directly exist for tobacco. You have already disregarded the main source (BoVD), and I would agree for 2 reasons.

1. Most civilizations don't make tobacco illegal
2. I've never smoked tobacco that potent that a saving throw would have been required to avoid negative effects.

However, if you want some mechanical impact and not just flavor, you could look at some of the weaker alcohols present in the game to see what kind of FDC you'd need to avoid "addiction". Again, tobacco addiction isn't the worst so even if you are forced 2 days without the worst thing to happen is you'll probably be a bit snippy with people (-1 or -2 on diplomacy cks?)

I like the feel you're going for for this character but I'd probably just stick to knowing the price and maybe going with what @Cow of Doom said as far as giving people a chance to notice hiding based on smell. (not guaranteed, but if they fail spot/listen maybe they can have a "Scent" check (Wis roll +1-+5 modifier depending on strength of tobacco smoked and last time it was smoked.) BTW, pipe tobacco does have a MUCH stronger scent than regular rolled tobacco.

Sidenote: possible "flavor" text, wiz/sor casting prestidigitation could alter the flavor of tobacco making it have a unique flavor!..the possibilities are endless, but it would definately increases the cost of tobacco if purchased that way. However, your party member could always burn a 0-lvl spell at the end of the day for you! (Side benefit for party members, it makes a nice aroma which is way more appealing that burning regular tobacco!)

Full Dragon: Not until very high level/with high level friends; probably a poor plan

If your character has access to someone who can cast True Polymorph, the caster can transform your character into a dragon with a CR equal to or less than your level.

If you're casting it yourself as a 17th level Wizard or Bard, that means you have all the Adult Dragons avaliable. If someone else is casting it on you and you're a lower level, Wyrmlings are CR 3-4; Young are 6-9, Adult are 13-17.

Note that this will remove your class and racial features. If you're high leve enough to be able to become an Adult dragon this is normally a poor plan given you can throw around Wish/Miracle/etc and dragons don't (normally) have spellcasting.

Dragon-like: From starting

If you're happy being simply dragon-like not an actual dragon, there are several options:

Dragonborn

Dragonborn (phb p 32) "look very much like dragons standing in humanoid form, though they lack wings or a tail", have a breath weapon attack that they can use, and resistance to an element depending on what type of Dragonborn they are.

If you have Xanathars Guide to Everything, there are some Dragonborn-only Feats that make them more draconic, e.g. become tougher or improve their breath weapon (XgTE p74)

In the Feats for Races Unearthed Arcana (playtest material) there is also a feat that gives a dragonborn wings and a fly speed, but it is playtest material that did not make it into XGtE, so definitely ask your DM before you get set on having it.

Pros:

• Works with any class
• Gets the look right at the start
• Can get more dragon-like if you get feats

Cons:

• Doesn't improve over time unless you get feats

Draconic Bloodline Sorcerer

The Draconic Bloodline Sorcerer makes you better at talking to dragons, better at doing elemental things of your bloodline, gives you a thin layer of scales, and eventually gives you the ability to manifest wings.

Pros:

• Gives you most of the advantages of the Dragonborn feats just by levelling up

Cons:

• Is a class, so locks you in to being a spellcaster
• Only gets the wings quite late(14th level)
• Doesn't get most of the look