I think maybe our 6 year olds were separated at birth ... you just described mine to a "t". We have been focusing some on diet as I know with him it makes a difference. But, I also think it might be the age. (At least I'm hoping it might be because then maybe this phase will come to an end.) I'm wondering if some of it is my ds's way of letting me know I am trying to do too much (which in reality is next to nothing - maybe a combined 1 hour a day) and that he's just not ready for that much focused time.
Last night dh and I spoke with him about his day and how he'd design it if he could. At first there was no "homeschooling" included, but we let him know that hs'ing is something that will be done each day. So, he decided if he could design his own day, it'd start with TV (which makes us cringe a little ... dh more so than I), then hs'ing, then bike riding/scooter riding, then Lego's, then outside time for free play, with eating thrown in wherever it fit. I know dh is very much not into the TV in the morning, but at the same time I feel compelled to try it for ds ... so we might today and see how it goes.
But I so hear you ... yesterday we were sitting on the couch because I was going to read aloud to him from a picture book on ancient Egypt and he was whining/complaining/being attitude-ish, and in my head I kept saying, "Do you want to walk over to the school and enroll you *right* now???" We won't; and I don't want to make empty threats. But he was being a bit excessive yesterday and it made me realize I need to look at the deep, underlying reasons why he's acting that way and see if we can rework some things to help eleviate whatever he's feeling that is causing his attitude/behavior.
So when he wakes again (he already woke but it's too early for him so he's back in bed), I think we'll talk over his plan for the day, add in what we need to do (speech for ds#2 and grocery shopping), and see if we can make a schedule that all are happy with and then do it ... I also thik that within the homeschooling time, I'm going to try to offer up some suggestions like:
It's English time; do you want to practice your printing or do some phonics/spelling? For math, would you rather work in your workbook today or do some pattern block puzzles? ...
And then maybe he'll feel like he has some say over what he does even though I've pre-established acceptable choices that make me comfortable, if that makes sense. It's all an experiement and I'll let you know at the end of the day how it goes.