Do I think a marriage with him would last? I have my doubts. There, I said it. But marraige is always a risk. And so what if it doesn't work? Would that make you absolutely unhappy for the rest of your life? I would hope not.
Why didn't your grandfather leave me? God knows I wasn't esy to live with. You';ll have to ask him. I imagine it's for the same reason. Stay and survive. Find joy.