Any chance they could move to a graduated assisted living facility? Since she is still high-functioning, while he needs a bit more assistance, it could be a great solution. They could start in an apartment suite, with arrangments for some staff to come in on a limited basis during the day while she's away to check on him. Would also be a lot easier to get him to some activities that are done at the facility because they'd be right there--no car required.
Also, when (and this will certainly happen) he suffers another health set back and requires more care, it will be a lot easier to transition him into the part of the facility for full-time care, and she can still easily see him.
This worked extremely well for DH's grandparents. Like many, there was reluctance to leave their home, but it was a far, far better solution for all.

Have your mom change all the clocks so that they are on time despite him.

If he is a veteran you may be able to get someone from the VA or VFW to come over and visit with him sometimes.

She can lie to him about appt times. If he has a 10am doctor's appt, tell him that it is 9:30am. That way when he drags his feet and delays...he will still be on time.

As far as taking meds on an empty stomach and wearing shorts in the winter.....the dude is freaking *90*, let him live a little.

Is there anywhere he can go for a couple of hours a day to give your Mom a break and probably tire him out a bit? Like an exercise class, coffee with some other men or groups where people talk about the old days, military experiences, things like that. I looked into this for my FIL but his dementia was too advanced.

I'm dying to know what job an 81 year old woman has 4 days/week!
Sounds great.

A couple things
1. The "setting the clocks back" poster is brilliant. Problem solved. Even just 15 minutes will relieve a lot of her stress and he won't notice.
2. My Catholic Church has a whole league of people that are home Eucharistic ministers as well as support groups, home visitors, etc. I would have you call to inquire first and then make suggestions to your mom.

These are all really great tips - yes, they are Catholic and it's a good idea for him to stay home and watch on TV and maybe have someone bring him communion. And it's interesting that so many people have recommended having someone come over to help him socialize and take the pressure off my mom. She actually works 4 days a week and he's home alone during the day. Fortunately it's never been a dangerous situation, but he invites anyone in who comes to the door (Mormons, Jehovah's Witnesses, sales people, people offering to sell firewood or shovel the driveway, etc) and always has them stay and chat and have some Pepsi. He loves having company but it's probably safer and smarter to have it be someone we've vetted.