I have a friend whose husband married her knowing she had a debilitating disease with no cure that would only get worse. It was a version of ALS that eventually causes complete paralysis but not death. They had a couple of good years, and then he ended up taking care of her. She had laid all this out to him very honestly beforehand. But he didn't appear to regret his decision. He loved her and said his purpose was to take care of her. Very sadly, he died before she did, unexpectedly. But I don't believe either one ever regretted their decision to marry.
But whatever decision you make, I'm glad you have each other.