My husband says if I'd have went with him, he wouldn't have got so drunk...?

No you didn't do anything wrong by not going to the party, he is the one who made all the wrong choices at the party, he is a grown man and all he is doing is making excuses for what ever he did do, he may or may not have done something, if he did then he is just trying to set it up where he is not at fault for being unfaithful to you, he let his anger about your being a 'no show' be his excuse for getting drunk, if he wasn't drinking mixed drinks, then there would of been no way for someone to put something in his drinks - a highly illegal action on anybody's part, by the way - now would there? He went with the intention of getting blitzed, and he don't need to use you as the reason he drinks too much. He needs to look at himself and admit he has a drinking problem and do something about it, being a wife does not mean your also a babysitter to him. The fact he wanted to bring your child there, regardless of the fact she had school work to do, outht to show you where his feelings lay, regarding you and the family and his family. Tell him he needs to change, not you. If he don't, then leave him until he does.