I totally understand your problem being around drunk people, it's a thing that you get used to. After the 50th time people ask you, if you want a beer or the fifth drunk person on the party tells you "I really respect you for not drinking...That's real cool and all, but I just could not do that!" it's nearly entertaining to me...What really helps me is having something else to drink when I'm out so I don't feel miserable because there is nothing for me, but water. Water is fine though

Go to places with good juices, tasty iced tea or something else, drink that and it's okay. It at least works for me. It's like the difference between grandmas birthday and you having to eat the salad without dressing and grandmas birthday with everyone eating meat and you having some tasty vegan thing, it's just better and also changes the way, people react to you.
You could also try to find things to do that involve people having to use their mind, art, sports, ..., still alcohol is involved most of the time.
About the caffeine thing: I do consume caffeine. A pill before my workouts plus I like to have tea, espresso, mate and sometimes also energy drinks. As long as it is controlled and you can go without a day, I believe that's fine!