I dont even know where to start. You need a big think.
Noone has it all. You choose term time so of course you're only paid term time. If you want more earnings, you need alternative or additional work. If you're opting not to then yeah, less money is the result.
DH is his own set of problems. He isn't working 7 days a week and it's pig ignorant of him to assume you're his built in childcare and he simply drifts into their lives for the fun bits.
You could consider play date swaps, using day-out money for a holiday club or confronting your husband about his lack of responsibility.
But yeah, ultimately there are no easy answers and you choose your hard.
Personally I don't love working 40 hours over 4 days where I barely see my kid over those 4 days but then my DC has her dad doing the school runs and has that time woth DC and I do then get a day off to myself every week, can spend extra time with DC in the hols and then afford clubs 🤷♀️ noone has it all.
In your circumstances, I'd probably do playdste swaps. The kids entertain themselves at our house and then do the same at someone elses. It's exactly like the Motherland Drop Off Party invite 😆