CV, just a thought here...

If your H actually participates and continues to get support and help regarding the M "problems"...

Would you consider that he is "working on the M"?

Have you decided what you want, yet?

Yes, I know you are here and want to work on the M and I know you have suggested such, although it still appears you maintain your position of keeping the M intact only until your S graduates...

You continue to have a few choices and none of them are easy:

+ Actively work on yourself to help make the M better
+ Continue to "survive" the M until your S graduates
+ Consider that your M actually is already dead and continue on with D

Personally... I think the second choice is the easiest route...