I'd suggest you separate things:
I am going through a divorce.
So continue going through your divorce. You chose to end your marriage, and you have good reasons for your choice. I don't anything in this that will change how your wife treats you... .or if it does change, it would be for the worse, not for the better.
It is time to stop thinking of her as your wife.
Divorcing somebody because they have cancer isn't normal. Neither is marrying them because they have cancer. Stopping your divorce proceedings would almost be like deciding to marry her again, and you sure aren't ready for that!
Not sure what i would do if she was diagnosed with cancer.
What would you do if somebody else you know (not your spouse) was diagnosed with cancer?