I am starting to see some familiar stuff in your posts, Feb.
After DS was born, I suffered from postpartum depression. It was bad. What I didn't know is that WH was also falling into depression but didn't have the awareness to realize it.
He lived in our home, but pretty much abandoned us in favour of work and his other activities. When the A started, it just got worse. I was essentially a single parent and maid, along with having a full time job.
I started to suspect he was depressed, but he refused any help. He wouldn't go to MC with me or to IC. At least, until he realized that if he didn't go to MC, I was done. It was ineffective because he was dishonest with me and the MC, and still refused IC or a visit to the doctor.
After DDay#1, he immediately wanted to try and R, but broke NC soon after and the depression worsened. He became even more hostile with me and his moods were darker. I came home from work one morning on a hunch and he was unable to get out of bed. I was terrified he was going to hurt himself.
I can't remember which poster first mentioned depression, but I agree 100% that it can manifest itself in extreme selfishness. Mine didn't, but WH's did.
I am not making excuses for one bit of your wife's behaviour, but I am saying this because if you really want your marriage to work I believe there is hope if depression has played a role in the change in her personality. When WH finally got treated (medication, IC) and the A ended, he became much more like the person I married.
My experience with WH is that his depression was like a vicious circle. He was depressed, and his self-medication was an A. The behaviour was abhorrent to him, but that made him more depressed. I also think after a point it becomes a self-fulfilling prophecy: I'm a bad person, so I do bad things.
I think it is reasonable for you to refuse to make any commitments until she has agreed to seek help. I would make that an absolute condition of R. IF you still want your marriage, there absolutely is hope, but you need to have very clear boundaries.
I will agree to disagree with posters who feel a hard 180 is warranted here. It appears to me that your WW is close to, if not at, rock bottom. This may be enough for her to start to get better. Have clear boundaries, for sure. But, if she is at bottom and is willing to get help, then I think talking together is okay. I would avoid expressing any wish for R though. You said it best, that the person in front of you is not who you want to be married to.
Once WH's meds and therapy started to kick in, I was able to support him in that. However, I never did go back to trying to help him manage his guilt over the A. It is not your job to make her feel better about the destruction she has caused. If and when she starts to de-fog and become remorseful, if you still wish to R, you will need to be able to accept her efforts but not do the work for her. Truly, as a BS just being open to WS's efforts is hard enough work without trying to do their job for them.
(((hugs))) to you and hang in there!
BTW - sorry if this post is a little all over the place. I had a lot of stuff popping into my head as I was typing. Hope you get the idea...