I presume you are still unbaptized. Keep it that way.
Don't be argumentative and don't express opinions contrary to his belief system. You can ask questions, but always remember that you are playing a game of psychological warfare, that you haven't been trained for, with someone who has been trained for it, so be careful not to portray yourself as Satan's Minion.
Because I never got baptized, I managed to maintain a civil, but dysfunctional, relationship with my parents until they died. It wasn't easy, but it was better than some of the dragged out train wrecks that I know of.