I am not the OP but I have a 7yo. She is awake for 13 hours a day, give or take.........There is plenty of time to play, be bored, be outside, be creative AND do a couple of worksheets. Its not one or the other.

In a power struggle with a 6 year old, whether you win or lose, you've lost.

Drop the rope, OP. It's easier said than done, I know that.

The child is 6. He should be able to handle some worksheets without ramping up the temper tantrum. He needs a routine and a schedule. Of course, you can't force him to complete a worksheet, but he doesn't get to be disrespectful. Figure out a schedule and put it on the refrigerator.

I think the problem is the worksheets. Forget them. 6-year olds should be playing and not sitting down for worksheets.
Concentrate on him cleaning up after himself, brushing teeth- the usual stuff.
I have no idea why this country thinks you need school for 3-6 year olds who have no business knowing letters or numbers. It's not like they are ever without an adult.
The letters and number come so much easily at 7-8. Why all this pushing at 3-6? At 10, one cannot tell who knew their letters and numbers at 6 and who didn't.

OP, it sounds like you need a break from being the primary parent of your 6 yo. At that age there shouldn’t be these kinds of power struggles because you, as the adult, have the means of managing behavior and enforcing consequences without it. It sounds like you are burning out, though, and are falling into bad patterns with your parenting. Under those circumstances, a great solution could be for your husband to step in so you can get a break and he can get your 6 yo back in track with a cooler head, it that does mean your husband has to fully engage, he can’t just swoop in to defuse one moment in a way that undermines you and then never follow up or take over the situation.