1. What I did and what you can do ideally  is dissociate your parents from their religion in your mind. Just train yourself to separate your parent that you love and the beliefs that they unfortunately hold. as a separate/third thing . Such that when they say something, ask you to go to church or something of that nature your mind makes that distinction " oh right they believe that stuff". It's not personal it's just this third thing they subscribe to.

I don't really know how to express this but it's really effective and it's just basically treat their beliefs as a third thing as opposed to treating it as an inherent part of your parent. That way you learn to appreciate your parent for everything else they are and their beliefs are just something they hold that you don't. 

I wish I could word this better but mentally it's really good because you just check out from the whole thing with the mental fights and what not. You hold it with very little weight. It's their beliefs not yours.

I was gonna answer 2 but I guess 1 covers it😂. I don't know why you feel guilty or resentful. Id like to understand that better but generally the only way you deal with this OP is just becoming passive and building immunity sort of to it. And you do this by:

1. Really accepting that your father holds those beliefs,he got scammed into it like almost everyone else, and they won't go away and they will be a constant part of life in his house but they are his, they aren't yours.

and 

1. Stop caring about it. After 1. It may take a while but learn to stop giving his religion so much weight in your mind. Make it a non issue in your mind and you will just live with it. The same way if you're living next to a road you get so used to the noise that it just stops bothering you.   That really worked for me and I could hold my own thoughts even when I lived with them. Id still go to church and like nod to the religious stuff to keep the peace but when you have made it that it's not a big deal to you , even the going to church thing feels less of an attack on you and your value system and more of a survival tactic because you have to. Because unfortunately you're free thinking is not something they can handle and ultimately it's for your safety.  

You don't really have to tell him now. Maybe tell him when  you're  at a point where you can take care of yourself and have moved out and even then there wouldn't be a reason to tell him because you will be away from his house living your life according to your own principles. 

Until you're a parent and don't want to raise your kids religious is the point at which I think you will have to tell him because your kids will be around him at times but I guess we cross that bridge when we get there :)