"His love for me is beautiful..."
He wants to deal with this on his own (strong) terms, and not have your own life completely derailed with his illness. It's a gift. He is not rejecting you, the illness has come between you.
Since it's progressive, there is little you can do practically , except suffer along with him, so why have two of you suffering the illness. You will suffer, with help, the loss.
I can relate. A burden to my family, is much worse than my illnesses themselves. They don't like my Stoic approach, but respect it.
He may just be the type who wants to deal with this privately. I know for me, dealing with "concerned" friends and relatives is draining.
"OK. Everybody go home. There's nothing to see here."