I have a few guesses....
1. Ron doesn't dislike you, he is just socially retarded. He might not even realize how unfriendly he is, he's just toally bad with people. Your boyfriend has probalby been friend's with him for so long that he's just used to his oddities. I bet if you casually ask around you might find out you're not the only person who thinks he's a bit off.
2. Ron is scared of girls. Therefore, even though you're his buddies girlfriend, he still doens't know how to act around you.
That whole making Brian and himself dinner and not making you dinner was SO rude, I would have said something for sure. I would have been like "What the F Ron, nice job. Way to drop a subtle hint."
I think that is the type of stuff you should say. Be really blunt but in a sarcastic way so it's as if you are just giving him shit and don't really care all that much yet are still calling him out.
That's how I tend to be in general and I've never had a problem with anything like this so heck it should work right!
I would be honest with your boyfriend and just tell him "Look, it's obvious to me that Ron either doesn't like me or is uncomfortable around me for reasons I don't understand. That's unfortuante but it makes hanging out with him less than fun. So, you can understand why I wouldn't want to be around him all that much." If he accuses you of overreacting or being wrong just tell him "Overreaction or not, that's how I feel and that's how it is."
As for this car ride, I would lay the cards on the table from the get go. "There's no smoking in my car, and there's no using chew in it either. If you don't like that, tough shit." If they say they shouldn't be taking your car then tell them you shouldn't have to sit in any car with someone with two disgusting habbits for 12 hours in order to accomdate someone else's gross addictions.
Sooner or later you might just have to be tough or be kind of bitchy but I would just let both of them know where you stand. Why should you have to put up with all of the crap?