I have had to deal with similar situations with visiting parents for the holidays. It really really sucks. I have a couple of suggestions but I don't know how much they will work for your situation. If you have a friend who lives around you, see if you can bring a friend to your family activity. Ask your friend to help you out. You sit on the isle and have your friend sit next to you.

Keep up with getting out of the house. See if there are things you can do while you are out to help the family. Makes you seem involved without having to do things with others. Suggestions: running errands, grocery shopping, pet care etc.

I know that you are atheist, but could you try going to church with your family. You don't have to listen to what is said or believe it. Just sit there participating as little as possible and think about other things. It can be painful to be there, but think of it as when you spent time in your most boring class in school. What did you do in those classes? There will be a lot of other people around and often people behave better in pubic than they do in private.

Do you have siblings? If so, can you do things with them and get 'family' credit? Can you stand being around them?

Good luck. Family sucks. I hope that you are able to get through this and back to your own place soon.