He does sound a bit like mine, literally did not give a fuck about being told off (by me or her dad) wasn’t aggressive towards other kids at all though, would actively avoid them. I had PND and took everything personally as well.
She has always been and still is extremely headstrong (if she didn’t want to do an activity at nursery she would just look at it and walk away), bear in mind she would constantly quote her teacher and want to look at pictures of her teacher, literally adored the woman but still couldn’t bring herself to do something she didn’t want to do.
Similar with illness as well, she never complains, seems you only find out after she’s gone for an extra long sleep that she was poorly never answered questions until she was 4 (which I think is normal).
We really had to keep calm, keep strong boundaries, “explosive child” helped us figure out what her trigger points were (it’s directed at much older children but by god was it helpful in clarifying our understanding). She was a little monster at home tbh, just a ball of fury. By 4 she was 90% ok to good. Still headstrong but much easier to communicate with.
I honestly don’t think he sounds exceptionally terrible (I obviously have a erm a low bar). Dd did need more intensive parenting than some other kids. I even asked her very experienced teachers about ADHD, which they said no to.I do think a part of it is just personality and partly is just the lack of executive control they have at that age.
To reassure you at 3 I was crying in the bathroom quite a bit, at 4 DD was positively delightful most days. It’s hard, really hard, but you do your bit and trust that he’ll grown into it.
I also found being silly really helped. After an utter screaming meltdown with snot just flowing down her nose I said,” I think a snail has moved into your nose, come out snail, you can’t live there!”(I was furious by the way so I was trying to calm myself and her). It gave both of us an out from the anger. It’s really hard to exit anger but you need to sometimes build a golden bridge for your child to retreat over especially when they aren’t the type to back down.