I'd probably quit, continue with the current freelance, and after a couple months of decompressing, start looking for some additional work. More freelance clients, "barista" FIRE (substitute teaching, dog walking, whatever), or whatever you can find. Or, if you find that the break has refreshed you, then look for another full time job and use your money to buy you the luxury of not having to take a job that isn't a good fit.
However, when I gave my notice I'd also offer to continue on part time, on an hourly billed basis for a max of 20 hours a week, at roughly 150% of the current hourly wage (but they will be saving money presumably because your benefits will be cheaper). Also, if there's any part of the work you especially hate, specify that you won't do that. Assuming this won't make you miserable, it seems like a great compromise. And the worst that happens is that they say no, which is fine as you were willing to quit anyway.