If you know it's abusive then you need to get out now. There is no reason to stay and it will become more dangerous as you wait. I suggest maybe waiting after the wedding a few days if that is possiable for you.
Then telling him politely that he needs to stop or its over. Which you probably need to end it. He's not going to be very happy, so I suggest if you need to leave immediately then leave. Have a ride ready or something I'm sure if your parents are able they would wait for you to get to the car. If it was my son or daughter I would seriously wait for them.
For the wedding I would just go and be polite, if he starts yelling don't argue back and just make him look bad in front of everyone. I doubt he will start anything and if he does hes not too bright.