I completely understand how you feel....
My boyfriend of a year and half now was diagnosed with grade 3 brain cancer (less than 5% survive over 2 years)
In the beginning a lot of people his parents included questioned why I was sticking around, not leaving him. It never crossed my mind actually. He asked a few times if I was going to leave him
I knew from the day I met him I wanted to be with him and his cancer didnt change that. So for the past year and I am hoping many more (but I dont know) I have been with him and I love him so much more.
I am terrified to lose him it scares me every day. I dont want to be alone and I also cant imagine not being with him. But that doesnt mean I will leave him.
Its hard and it sucks and I just try to enjoy what we have now. He is doing so well with the treatments I hope your husband is too. Just reassure him and know he would do the same.