I'm not sure if this is the right place but I'm not sure what to do.
DS is 17 and was diagnosed with global development delay and has some behaviour issues. He functions much younger than he is at some things, emotionally he's around 13/14. He doesn't listen if we tell him to do things like tidy up, we have to tell him multiple times and he still sometimes refuses. Giving him stickers and rewards used to help but now he's older he isn't interested. He can be hard work at times which he can't help, he needs me to be much more involved than I would be if he was NT. His behaviour is a bit better than a few years ago, where he would be violent, hit me, throw and break things etc. He still does this but not as often as I try and avoid situations where it's likely he'll be like this. The main trigger is if he can't do something and he doesn't understand but when he's calm he apologises and just wants hugs. He was also late starting puberty, he didn't start until he was 16 so is in the only a year in which means a lot of hormones which doesn't help.
DP moved in just over 3 years ago by this point he had met DS and had an idea of what he was like but I made sure he knew all about his behaviour. DS was happy with him moving in and they got along great. DP doesn't have children of his own.
Over the past year, their relationship has suffered. He gets annoyed at having to repeat himself when telling DS to do something which makes DS refuse even more if DP is shouting at him. I'm always stuck in between them. DS is also quick to get angry because of his hormones. He moved to a mainstream course at college and he started a few weeks ago, he's getting but since then he's been refusing to do things more often and giving us attitude, which I assume he sees at college.
Yesterday I found he’d been searching for porn. He didn't see any of it as we have parental controls on his devices. I asked him how he'd heard it and he said at college. I don't think he understands what it is so I told him not to search for it, I was shocked. I know I probably didn't handle it correctly.
DS was trying to search for it again today and I kept trying to redirect him but he continued. DP then told him if he didn't stop he’d take the iPad off of him. He didn't listen so DP took it which led to DS throwing things and getting very angry. Hitting, pushing, spitting etc. When he's like this nothing calms him down. He eventually calmed down but was crying and asked DP for a hug, DP said no because he was naughty so I gave him one which DP thinks was wrong as I was ‘rewarding’ him. He told me he wanted to go for a walk but not with DP so I took him out and he told me he doesn't want to live with DP anymore, or me.
He said he wants to live with his dad who lives almost an hour away and is supposed to have him every other weekend but it reduced to 2 Saturdays a month and he hasn't even been sticking to that. His dad doesn't spend much time with him either. He's often left to his own devices.
I'm unsure if his dad will even agree as he works long hours and isn't involved much as it is. WIBU to ask DP to leave?