Hi op,
I had a very similar child who is now the kindest, most thoughtful 17 year old who has no aggression at all. He's is super calm and causes no conflict. He is a very happy, outgoing teenager.
He is doing amazingly well at college and works hard at his part time job.
He is now by far my easiest child who causes no issues.
I NEVER THOUGHT THIS WOULD HAPPEN!
At 3 he had been kicked out of three nurseries and two mother toddler groups (one of which I ran and was asked to leave after he pulled a dummy out of another child's mouth and caused deep gouges out of her face! i was sooooo ashamed!)
if we went to soft play or a park other children would soon start running over to their parents crying as my son had been let loose and caused chaos - punching, shoving, scratching (he actually never bit anyone which was a miracle).
He and his older brother could never be left unsupervised or WW3 would break out within seconds.
we lost a lot of friends and even family were wary of visiting. we stopped going places, he could never go to birthday parties etc as he would just ruin them.
I cried so much, I tried everything I could think of and like you was at my wits end thinking this was his personality and would never change.
At 3 he went to a nursery attached to the school he would attend. Thankfully they didn't ask us to leave and worked hard on his behaviour. Although no major changes happened until his second year in primary (so about 5.5 years old) he started to calm down and make a few friends.
it was an extremely difficult few years, a lot of hard work, talking through feelings, constantly reiterating boundaries and acceptable behaviour and many, many tears but things did begin to change.
although he has never been formerly diagnosed he is definitely on the spectrum but as it never seemed to hold him back at school or life i didn't get him diagnosed.
the school did bring this up several times during his early years.
he is aware of this and didn't want to follow anything up either.
What i am trying to say in a long winded way is - this will pass, you are right in the middle of it all right now but as he grows and can understand things a little better he will slowly change.
just keep talking to him, when things are calmer. Have a little snuggle and tell him all the things you love about him and all the things he did well.
Every night at bedtime have a little round up chat and let him tell you what he's feeling.
Keep working on boundaries and feelings and don't give up! Keep on doing what you are doing.
He will come through it and one day it will all be in the past xxxxxx