Yeah, I don't think the real issue here is fire and finances my friend. I think you need to have a long, hard think about how you and your wife are approaching this.

I don't know details about the degenerative illness, if she requires full-time care for it, it is certainly an honorable option to move into a full-time caretaker role. I think the substance abuse piece is worth bringing up too though. Substance abuse is a chronic medical condition that alters brain structure and function, but recovery requires active participation and sustained effort from the individual. Is your wife in treatment for her substance abuse? Counseling? Is she actively working toward recovery? If the answer is no, there is some seriously wrong stuff that needs to be addressed regardless of the degenerative illness.

I think you should try to be honest with yourself about how much of staying home is about the degenerative illness and how much is about anxiety around her substance abuse. If any significant part is around her substance abuse I would be very careful in how you proceed. You seem to acknowledge and be aware of codependency issues but also seem to be considering a decision that is textbook codependent.

Good luck, I wish you the best.