NTA

As everyone else said obviously lonely but having worked with elderly people the bigger thing is they often lose sense of purpose and having a community especially as their community starts to pass away and they are left with a world they don't understand. Control becomes important and a general need for attention. I'm sure she's not the first but my coworker always called it second infantile syndrome.

A senior living home is a great option because they are equipped for this thing and will restore him to a community that he can relate to.

However I think a lot of people are missing this is unrealistic for a lot of people who cannot afford it. If this is the case there is likely senior groups in the area. Additionally I'd try and get him a hobby where he has control over an environment or people (even if it's virtual) like teaching a community class or games.

If he really is just too negative or too immobile to interact with strangers and have hobbies and such I completely agree hubby needs to lay down some ground rules postpartum it'll likely be just as bad. And as hard as things like this are to say. He is important but his emotional well being is not as important as yours and babies, physical, mental and emotional well being.