Depends on circumstances, but I would pay off the mortgage, if possible. Or some of it, to reduce payments. But only if it didn’t significantly reduce my savings, because I would want to hang on to most of it.
Then house maintenance, boiler service, ensure cars are serviced and winter ready. Maybe reduce to one vehicle.
Our househod heating is oil and wood, so I would get a full tank of oil and buy in a load of wood.
A dehumidifier and a Sheila maid, heated throws and a slow cooker, freezer and air fryer, if you haven't got those already.
I wouldn't spend out more on windows or solar panels at this time. It is possible to do a lot of DIY insulation around doors and windows. I have a sheet of bubble wrap hung on a wire like a net curtain at my bathroom sash window. It makes such a difference and also adds privacy. Heavy lined velvet curtains also work well.
I wouldn't take on a second job. Being poor is exhausting enough, and it also takes extra time, to cook from scratch, research bargains and shopping, mending clothes instead of chucking out, etc.
If your husband is unable to work, (even a part time job would help,) perhaps he could volunteer at a charity shop, with the chance to buy things like decent second hand clothes. But he should certainly be taking the main role in childcare and housework.
Totally agree with the resentment bit, as outlined above. Another reason for not getting two jobs.
You'll manage.