My son was exactly the same when I moved him to his supported living place.
It’s the drugs still in his system it takes a while for their personality to resemble anything near near nice. My son is about 6 months clean now and has only just started to be nice although I’m still not sure if it’s a mental health problem with him.
Perhaps just block him for a bit or decide your own boundaries.
Tell him u will speak to him once a day at a certain time.
When I had counselling and my son was right in the full throws of his addiction and my counsellor said about taking g back control and setting your boundaries.
So I would block his texts and calls and then unblock him at 6pm if i felt the need to i would call him. If he was nasty i would end the call and tell him if you want to speak to me nicely I’ll leave the call unlocked for a other half hour. If he called me straight back nasty and demanding I would block him again.
Yes he dirnt like it and yes I was still stressed as you are as a mum when ypur son is an addict but it did help and enabled me to live a bit more normally.
Your not cutting him off completely but setting reasonable boundaries. I realised now I was bullied by him and did too much…my.mum never drove so I always got a bus or train..he will just have to grow up and do it himself.