When my son tells me he hates me etc I don't react atall, so he ups his game to punching etc.
I can understand you not wanting to react, but nit reacting at all will make him think you didn’t hear him or dint care hence the escalation in behaviour. One thing I’ve found can help is to talk about hate, what does he mean, what does it feel like or how sad you are that he hates you because you live him very much. Anything that tells him you’ve heard him and that it had an impact.
In terms of him listening I really get the urge to shout (my 7 year old has developed selective hearing 🙄) but you know all that does is raise the volume and anxiety levels. One thing that has helped is me modelling listening to them, so I’ll stop what I’m doing, out down my phone or book or whatever, make as much eye contact as he can manage and listen to him. When I’m speaking to him I’ll ask him to put down whatever, depending on what he’s doing I might hold his hands, get down to his level and speak in very short sentences or give very short instructions. If he starts to get shouty I’ll purposely lower my voice, be very calm (not easy) and repeat what I’ve said.
It’s frustrating and you need to build in time for communicating even the most simple request but over time it’s got a bit easier. I also try to make time to just chat with both kids while watching tv, playing a game etc. Bed time can be a good time to reconnect if you feel things haven’t gone well. I’ll ask them how the day has been, and acknowledge that I’ve been a bit grumpy or shouty or whatever, and we’ll agree to start afresh tomorrow.
In terms of violence absolutely look for post adoption support, in the meantime it can be really useful to talk about it when things are calm in a “I wonder what happened there, how are you feeling now, how can I tell that you’re struggling” kind of way. He may not be able to tell you and that’s ok - it’s not about getting answers so much as letting him know you can talk about hard things.
Do take time for yourself, if your walk gives you much needed decompression time then take that time for yourself, if you have a partner agree to tag team each other so you both carry a bit of the burden.
Don’t beat yourself up though, it’s very hard and with each age, new challenges pop up.