family issues

First I need to give some history-I am one of 4 kids, two being from previous marriage. My parents divorced and got back together (yeah I know). They have been back for about 4-5 years now? The last few are littered with fights and threats to break up. I have really been calling  him out myself to try and keep our family together, but it's really wearing on me. There are 5 grandkids, my parents being their last living. I just feel like none of their problems are really that large, they just pick at each other. I know it's their relationship, but the implications of them breaking up again are so far reaching. I don't know that we can all go through that hurt again. 

My husband suggested that I keep them at a distance, which is hard since my mom is one of my best friends. He also lost his dad recently, so even though he says that he understands my concerns. My mom has a very rare cancer that has no cure. I know it hurts her when I tell her I can't help her anymore (emotionally with her issues) and that I can't be involved like this. My fear is that I'm hurting her and she will pass, which would be something that I would carry the rest of my life. But being her punching bag hurts me Day to day now and effects my relationship with my husband (who is seriously the best-he has supported me through all this family BS and loves me so fiercely)

My dad acts like this is not a big deal. That is almost as bad cause it's kinda like you're a father, when you make descions it's never just for you. It's for the whole family. 

I really need opinions from people who aren't emotionally attached. Thanks...