Frankly, I think your DH is selfish.
He brought children into this world, and he should want more for them. He should want them to be able to do things that they enjoy, have some summer fun, holiday experiences, if it's within the economic realm. He should expect them to live a miserly existence because he essentially had one and he feels he didn't miss out.
Many, many letters to advice columnists relay similar anger with parents who did this to children... prioritised themselves at all costs over their own children. Really shitty parent, imo.
I would put my foot down, tbh. He's being selfish. He can't expect his children to be like him; they're not. They sound like good kids. And his desire that they don't go on to higher education because he didn't and 'what's good enough for him should be good enough for them' attitude is the epitome of shitty parenting attitude, no better than people who don't want their children to do better than they themselves did ...
I'd go so far as suggesting that if your marriage breaks down over this crap, he'll be working until the day he dies for sure, as everyone will be split.