I know how you feel on several of these things. These I can offer sympathy and understanding on.
I have a mild form of autism, as well as ADD. I can deal with people in person, but I don't like it. Online, I can filter things down to a manageable level. Fortunately, I haven't had to go to a large party in years that didn't have the option of finding a small alcove and chatting with one or two people of similar interests.
Time to recharge is very important. I hope you'll be able to get plenty.
Also, what's with small talk? I do not see how talking about the weather, or the quality of the miniature quiches, without any objective, point, or reason is helpful, good, or useful. I also can't figure out how to properly do it without either sounding like I hate the person or like I'm trying to communicate in secret code.
I hate small talk.
My body likes to flip me off, too... but not as badly. I have to deal with what appears to be the starts of the same set of long-term musculoskeltal issues my mum has had for many years, a set that has no real name because the doctors have had no idea what it is. It may be related to fibromialgia. Basically, my muscles tense up, and will do like a slow-burning, less intense cramp for up to three hours... and everything is tight. I had to stop practicing martial arts due to that. Much less severe than what you describe, but I understand how hard and stressful it can be.
You are lucky when it comes to brain freeze, though. Your nose feeling frozen is not as bad as when it feels like there's a shard of ice poking up into your brain, most likely.
Brain freeze can hurt. A lot.
A.L.I.C.E.: "There's no need to apologize."