OP - A lot of that behaviour sounds similiar to what we were experiencing with our DS. I really feel for you as it is incredibly upsetting and stressful
. Dr's and Midwives would pass it off as normal if slightly hyper behaviour. His Daycare were concerned tho and mentioned a few incidents. He is usually not mean to other kids, but would sometimes just not even notice kids in front of him and barge right through. Our DS also had real issues with sleep (from birth to recently) and had a slight speech delay. He is very defiant and would have massive tantrums. He would bite, kick and hit too, but our main worry was/is his impulsive behaviour. We had locks on every door and gate and he would still find ways out and onto the road
DH and I were at our wits end. DS had a difficult birth and first 3 months, but nothing that should have seriously impacted him. He has eczema & refuses food a lot (although he is thriving). We managed to get a referral to speech therapists, who said they were not sure how to help as he would be great for them, but they could see he wasn't talking properly. They referred us to Paed. Paed said that yes he was displaying some unusual behaviours and it's probably a "pre-curser" to ADD (which I do have in the family). As he was only almost 3 he could not do any testing etc as ADD cannot be diagnosed until later. He sent us on our way basically saying - just cope.
On little sleep, pregnant with DD and having tried numerous parenting workshops and "experts" DH suggested we try a Naturopath (i am not really a fan of Naturopaths, but agreed). She said she believes he is Gluten Intolerant and possibly has a few other intolerance's. She was actually SUPER helpful. She also suggested trying fish oil to help him with the speech issue.
We went Gluten Free straight away and the change was noticeable within days. Within a couple of months he was talking much better, sleeping better and far fewer tantrums. If he would eat something with gluten he would have a meltdown. It was REALLY obvious (even other parents at playgroup noticed). We saw our new GP (who was much better than previous Drs) and asked whether he should have more comprehensive testing and she said seen as it had helped already she didn't see any point for now (considering I was pregnant and moving OS). We will stay GF and when he gets older we will see if we can do testing to ensure we have covered all bases. He still has behaviour issues, but compared to before it is almost normal 3yo behaviour.
I am not suggesting this is what is wrong with your DS by any means, just saying that we left no stone unturned. Neither of us ever thought Gluten would have that affect on our child. I was the parent who never let him have junk food, grew my own veggies, limited his sugar intake and was careful about food colourings/flavours etc. It's so frustrating when people say "He is just a boy" or "It's terrible 2's/3's etc" or worse they assume you give him Junk food and red cordial
. Our instincts told us it wasn't normal and we fought until someone listened. It wasn't normal and we now have a much happier little boy. I really hope you can find they help you need too.