He tends to go harder on his birthday, and all his drinking mates will be at the party as well
My first thought was then don't go and take care of "you"
My second thought was go for a while and then leave, but then I know me I would be so uptight that everything would be a reason to get mad.
KI- gave a great option I like.
I would suggest don't do anything until you can make a calm decision.
These are things that will always come up in the future and thinking in a calm state will help with making a rational decision.