I'm not sure if this is the correct place to post this but I don't know what to do.
SS is 14 and he has developmental delays/possible ADHD and he acts younger than he is most of the time. When he is happy, he is the sweetest, kindest child but when he is upset he is violent, hits, breaks things etc.
I've known him since he was a toddler but I was with partner for 5.5 years. We get along great and he did with partner too. We are splitting up due to him having an affair and have told SS that we are no longer together and I will be moving out soon.
Since then, SS hasn't been doing things ex has been telling him to do (he struggled with that anyway), they argue about everything and ex is constantly getting annoyed with SS.
Yesterday, they spent the whole day arguing and ex wouldn't back down as SS is rude and wasnt listening (to simple things he was asking like tidy up, having a shower, go to bed etc). SS was angry so was acting out more, he wouldn't go to bed so ex threatened to take his iPad and SS threw the iPad at ex and was kicking and saying he hated him.
I managed to calm him down by hugging him and ex said I was being too soft (maybe I was but it worked). Although he is still saying he doesn't want to live with ex and he hates him.
Just to add, he lives with us full time as his mum struggled with his behaviour as she has other children, she works a lot and lives an hour and half away and when we moved we agreed it was best he lives here so he didn't have a massive change in routine. She sees him 2 out of 4 weekends a month but it's getting less and he's much happier here anyway as at his mums he's left to his own devices and acts out to get her attention by hurting the other children and breaking their things.