Easily answered questions:
#1: Because they regulate tobacco, I think they probably would.
#2: We arrest the dealers and seize their drugs, possibly for redistribution. (Here's another simple solution: We introduce, commercially, a large variety of types of marijuana of varying strengths. We do this already with tobacco; cf. cigars, where you can probably find, if you look, all varieties from double claro all the way up through oscuro.)
#3: Use and possession, possibly cultivation if people actually get their hands on seeds.
Really, adjusting laws is probably less of a problem than you're implying, and absolutely not a reason to not legalize. Any costs will be paid for by the revenue generated by marijuana taxes and reduction in costs spend on regulation (because those costs will be reduced, unless the government ****s up REALLY badly).
Nice ad-hominem later, though. Why don't you ask Paul Armentano at NORML about that and find out how wrong you are. In fact, you don't have to: read
these arguments. That's a lot of work and legit scientists on a case for something that's, in your words, "just [because they] want to get stoned and not have to worry about being thrown in jail for it."
I would maintain that that's a different issue (supporting the artist).