I can't stand mine either. Ditto on the "they treat DH like dirt." It breaks my heart.
How do I put up with my IL? I go to every family event that DH wants to go to or wants me to go to (ie a baby shower just for the women). I go, I sit there, I smile. If I am asked a question, I respond very neutrally and then ask a neutral question back.
Do you still see them? We do see them, but on a limited basis.
Do you wish that you could cut them off? I do not wish to cut them off. I do wish for them to treat both DH and I with respect, which is what I am working with them on.
What do you do around the holidays? Our families live far apart, so basically for Christmas we do eve with his family and then day with my family but stay with my family for a few days. Otherwise,the 4th of July is with my family and our family friends. Memorial Day and Labor Day are up in the air. We usually don't celebrate Thanksgiving and Easter with family - just friends here in town that also has family far a way.
In the long run, I think that every relationship has give and take. I also make sure to remember that these people ARE his family. You can't chose your family. However, you can choose your friends. So as long as you have friends that can fill in the family gap, I'd put up with the IL's and celebrate the good friends you have in your life.