PC, let me reassure that if there was a second adult in the house your ds1 would be diverting his wrath into playing you off against each other, because that's what mine is doing at the mo.
Backchat, dreaminess...sounds very familiar.
Do remember too that at this time of year, the nights are short, the evenings long and light, by Year 4 they expect to be able to watch key footie even if it is a school night...the school year is drawing to a close.
I think many of us could have written your last sentence. YOU ARE NOT A BAD PARENT!
I have found the following strategies have worked OK in recent days:
Find a time, if possible, when it is just you and him (does ds2 do any activities solo like Beavers etc?)
Pour yourselves both a drink of choice, try and make him feel you are having a meeting that you will both contribute to
Draft an agreed contract of reasoned essentials (ours includes latest bedtime for school nights and weekends, screen time, household chores). Get him to take ownership of the outcome and make him discuss the pros and cons of any diverging opinions.
Once you both agree, then tell him what, if any incentive you propose if he sticks to his side of the bargain. I suggested extra Wii time at weekends and that was snaffled with alacrity.
The other thing that I have noticed always winds ds right up is his dad's well-meaning tendency to be on his case on school mornings. He reminds him several times to do the same thing and quite trivial matters escalate very upsettingly for all concerned.
While I know it is enraging to see a little boy mooning about in his room with a bare arse and one sock on, I consistently find that telling him if he wants breakfast and not to have to walk down the street in the nude he has to be downstairs and ready to roll at 7.40, just once, firmly, works. Does your ds1 wear a watch? Remind him to keep an eye on it and then leave him to it. Then I call up, once, at 7.40, and...he is there, sort of dressed, usually.
Don't forget to explicitly appreciate his helpfulness and good attitude when he gets it right. When they are this horrid it is sometimes easy to overlook the fact that some of the time they do as they are asked!
HTH
PS if he gives you the bird about what his dad lets him do/get away with, just say, My Gaff, My Rules, sonny.