Quote: I know I need to just accept the fact that maybe there is nothing I can do to fix this
Whoa!! It's WAY too early to know that. You're trying to peek at the end of the book to see how it all comes out. This is a process and you're going to have to go through it.
My late husband and I used to have a saying when facing something unpleasant: "How do you eat an elephant? One bite at a time." You've got a big old pachyderm on your place and it's going to take a while to get through it and digest it. I know it's hard, but right now, try to stay in the present and avoid imagining what might or might not happen. And especially take care of yourself-- rest, diet, exercise, see your friends, rent movies you like. You will live through this, but it might be a long process. Other people have gotten through it, and you will, too.
Also stop trying to figure out what he is going through, why he is going through it, what it means, what you might have done differently, etc. Just focus on YOU. All of your worrying isn't going to change where he is at right now. Put your energy into yourself. You will survive this... read the signature line at the bottom of my post. Print it out. Memorize it. Post it somewhere where you can see it all the time. It's true.