Speaking from my own experiences, I'd say this could be normal. I'm going through pretty much the same thing right now, particularly with my Co-F. Until recently, Co-F was NEVER self absorbed. He went about his life acting dopey and clueless, completely controlled by NM, and never engaging in any kind of serious conversation. He's always acted in a very Forrest Gump "life is like a box of chocolates, la dee dada doo," manner.
NOW, in the last two years, he has REALLY changed. My NM was diagnosed with terminal cancer and one month to live (allegedly-I've seen no proof of this and she's still alive). After that happened, Co-F became very self absorbed, making every single thing about himself and his dying queen. He has stopped asking people how they are feeling, and instead forces upon them how HE is feeling (and he's always feeling sick). They have also alienated most of their friends/family. My NM's sister (my Aunt), who has stood by her and tolerated her for decades has finally stopped visiting. She's now in her 80s, and I don't think she can take it anymore, especially now that it's coming from my once pleasant father as well.
This is an example of how my father has changed, in just a short time. He turned 80 last month, so the woe-is-me stuff has been cranked up a notch.
Typical phone message, ten years ago:
"Hi! Just calling to see how you are. Hope you're doing well, and enjoying the new house. I sure look forward to seeing you. Pet all the dogs for me. Have a nice day. Bye."
Typical phone message, today:
"Just calling to say hello. Things are going terrible for us. Your mother is going to die any day, and I'm not far behind. My arthritis is terrible, and I have to have a test for my prostate next week. I'm going to need surgery, not that it matters, because I'm going to die soon anyway. We're just miserable. Oh well, just thought you'd like to know."
As far as I can tell, my father is extremely fit and in amazingly good health for his age, so this is the effect of life with an N-wife, not Alzheimers or other disease.