You want to leave your husband? (maybe i'm on the wrong track here, if so ignore this post)
If i have interpreted correctly, you seem to say that this is because it is difficult for you to live with a reminder of the pain not only your husband suffered, but your siblings suffered, and also you suffered. It is understandable to become overwhelmed and want to distant yourself from things that hurt you, it is human not to stand too close to a fire if you are hot, so please don't feel guilty if that is what you are feeling, but hopefully there is room here to take some time, stand back, and see what is going on, and exactly what would be resolved, achieved, or put to rest by the actions you chose to take.
From what you describe, purely from this post, it is clear that there is a lot going on at the moment, it is not a matter of standing too close to a fire, it sounds like right now, things are just heating up.
I'm sure you are quite confused and uncertain on how to support your brother through this rough time, and it is no shame on you to feel overwhelmed. You sound like you have a close loving relationship with your siblings, and you speak of your gratefulness for your sisters protection when you were young. You have also talked about the situation with the arguement between your sister and father and you stood up for your sister.
There is a clear potential for good in the relationship you seem to have with your siblings, but i sense a continuing need for approval by your siblings from a man that claims to be religious and even now seems to be trying to hold onto some power by the things you said he said. It must be very painful for all of you for him, and your mother, to continue to deny the things that they did.
I see the immediate issue here to be one of gaining some resolution in this situation, for you and your siblings to get together and discuss your minds, because the truth is that your parents now at this age will probably never show any sorrow or admit their guilt if they have not already done so. This doesn't mean that there can be no sense of justice or closure, it is a matter of finding a piece of mind and communicating with your siblings in an open and truthful way. What happened is not acceptable and it is not your shame or your siblings shame. It is just my opinion that what is going on here is that there are unresolved issues, and an enormous amount of frustration in the injustice of this situation, especially when no admittance or explanation is ever offered, and that kind of thing can stop you in your tracks and make you want to bail in some attempt to escape the pain, but running away doesn't solve problems.
All i'm suggesting, is that before you make any rash decisions, first see yourself through this rough spot, because although i do not know anything about you, i know there must have been a good reason why you got married to this man, and he had a good reason to marry you, and you show guilt at the pain he endures in reaction to you, but believe that i'm sure he endures that pain gratefully.
Also, on the other side of the arguement, there is also no reason you should feel bound to your husband if there are other circumstances that compel you to leave, you do have a responsibility to yourself and a search for happyness. If you do find yourself very much in need of a break from your husband, perhaps that is something you could discuss with a marriage counsellor.