Oh @MrsJonesAndMe sorry you're struggling today, it does sound like your DH needs a kick up the bum.
It really is not the end of the world if DS takes some time off from schooling, it just isn't. Every kid out there is in the same boat and they will catch up.
I was chatting to a school mum who's kid is same class as mine and has gone back. They are spending all day playing, no worksheets, no learning, no new content. They go home each day with a stack of printouts and the instruction to do a few at home if you can.
We're still doing our alternative style home schooling, which takes up a couple of hours a day, then we're working on encouraging DD to self entertain away from the TV. She has billions of toys, I know because most of them are on the floor :D every time she says she's bored we remind her that she has stuff to do and just needs to think about it and choose something.
Your DH needs to pep up and start taking some of the responsibility during the day, he could at the very least use his lunch break to take DS to a park or garden or something and eat al fresco.
Hope things pick up for you, don't feel bad about the toastier, my lunch was pasta with butter and cheese on and a Cadbury's Oreo bar.