My DD (3.5) has just gone through a phase of this. It was hideous.
With DD it was an independece thing - she stopped wearing a nappy at night (her decision one night that caught me completely unawares) and I think decided she was a BIG GIRL.
From then on she point blank refused to do anything I asked - after bathtime she'd run, wet and cold and hide under the table shouting Noooooooooooo to the towel, clothes etc, like a little wild animal, couldn't clean her teeth, dress her, brush her hair, get her in the car etc. It all happened overnight and I was completely floored.
Giving her a lot of control really helped - she chose a new toothbrush and toothpaste and then started to clean her teeth again. I let her pick out her own pjs and put them on (inside out and back to front of course ) and got her to choose clothes in the morning.
Before - she didn't give a stuff about any of this and was almost the opposite in wanting me to do everything.
We've always had a struggle at bedtimes. It's been our bete noir. I loathe bedtimes. At the moment her bed is in our room, it's been the only way I've been able to get her to go to bed and sleep. After a couple of weeks of this she's now started to come out repeatedly again.
I have a tigger toy with a sticker chart on it - when she gets 7 stickers she gets the tigger. So far after 4 nights she's got 2 stickers - it's not quite incentive enough. She got those because she was poorly and went straight to sleep! We've also tried sweets in balloons that she can pop to get the sweets in the morning if she doesn't mess around, it worked for 2 days. A normal sticker chart didn't work, not exciting enough (trip to zoo after 10 stickers - took us months). We also start reducing the number of books I read and then the final one is removing her tv time.
I'm off to the shops this weekend to get a snazzy new den bed, I'm hoping this will lure her back into her room and encourage her to stay there. Most nights she messes around for at least an hour, then gets up in the night and finally gets me up at 6.
I think you're doing everything right by the sounds of it. I found that DD would also eventually comply if I refused to give her something that she wanted - ie you can have your xzy when you are dressed. Come on let's race!
What happens if you give him a choice in the morning, or if he misbehaves and you turn your attention exclusively to DS2?
Do you think it's attention seeking or independenc e or just toddler?
I was going to suggest ditching the pull ups if he fins them so offensive(expensive habit if he keeps ripping them off) and really going for the potty training, but not sure if now is a good time if he's being so wilful.
I completely sympathise with you. I found this phase a total nightmare, and I only have one to deal with.