My SO is in a very similar situation - been at company for 5.5 years now. Each of your points I said "Yep". He’s got the cat for company. And he tries to make calls rather than instant message people so he’s at least speaking to someone. It’s the same stuff for work each day, but he breaks it up. Goes out to lunch on occasion with a buddy, or one will stop over to chat for an hour with him, he goes for walks to local parks, and he might have something going in the background (tv turned down, or someone on Twitch tv always talking – this greatly helps with the feeling alone for 8-12 hours a day while I’m gone. He will participate in the chat room every once in a while so they do actually talk to him, so it’s a nice way to keep “social” when it hits that there's no one else to talk to). He’ll do his workouts, laundry, showering, cleaning – it’s enough to break it up. We need to figure out how to keep the work “at work”/in the office area because sometimes the day is not over, even when I get home, and people still have questions/issues while we’re trying to do our personal stuff for the night (I’ve thought about getting a locking door knob for the office door, and once he says “I’m done for the day" I go lock the door and swallow the key. We’ll need at least 2 copies of the key.) But I hope some of the above suggestions are helpful. (I'm kidding about the latter part of that key bit)
To answer your question, as sucky as the situation is, he can’t take an office job without at least 75-100% pay bump, probably more. The work from home perk means he can go and visit his mom for 3-5 weeks each year and work from her home, instead. He works during the day, hangs out afterwards and on weekends. Does she have a surgery coming up he can be there for? Did 96 year old grandma have a fall and break a hip/have another health issue? He can be there to say goodbye, etc.. If he were to get an office job, he’d lose that, hardly ever see his mom (who lives 1,000 miles away), wouldn’t get to help out around the house, couldn’t visit his parks or his buddies, have to go get some more business casual clothes to wear, work normal hours (and deal with traffic), etc. So it’d require some real cash to change the situation. This of course may change at any point, but works for now.