Wow. The answer is very individual and probably so complicated that you should work it out with your therapist. You don’t have control over your emotional reaction. You feel how you feel and that’s neither good or bad. The question is, what choices you will make in his presence to make sure you don’t do yourself or your family an more emotional damage. No one can answer that for you really. Maybe the best answer would be to just avoid those situations, but that could cause even more family drama, I don’t know your family dynamics to be sure. Maybe you create a calming ritual that you can run into the bathroom and do. (It will take some practice to bring yourself to a calming place in 5 minuets but it’s possible to learn if it’s important enough to you.) Sometimes situations just suck and there’s no real easy answer. I hope you figure out a way to come to a place of peace about it. I heard a quote that went something like, “Living in unforgiveness allows a person to take up space in your head rent free.” It sounds like you’re nowhere near being able to forgive him but remember that as long as you hold onto your resentment he still has power over you. I have no idea of the correct process of giving up resentment though, that’s why if I were in your shoes I’d spend a few session with a therapist.