A therapist shouldn’t tell you what to do, just provide a safe space to explore your feelings, work through all the relevant questions you can think of, and maybe help brainstorm if you can’t come up with your own options.
Your wife and daughter’s situations are relevant, but so is yours. If your wife isn’t in love either but neither of you want to divorce, it sounds like your options are to either work on repairing and rekindling the marriage within the constraints of her diagnoses, or mutual agreement to keep the marriage going for now but see other people. Both are full of challenges and risks. If she’s not ok with either of those, then you may have to make a decision for yourself.