OP, I was in a very similar situation with my eldest, actually quite a bit worse. As regards phone usage, I wouldn't consider that a battle worth having, I understand why you do, but it's such a flash point for you. I told my son that he needed to get a part time time job to fund his phone when he was 18, which he did.
My son threatened us with the police many times, I told him he was free to do as he pleased, but he wouldn't be coming home. It seemed to put him off. He was about the same age as your son.
I would labour the point that although you love him, and always will, he cannot treat you the way he does and will be expected to leave 2 weeks after his 18th birthday as you will not be legally responsible for him anymore. Stay calm and tell him you will not abandon him, and will help him find a place of his own. I would also tell him that he is of course free to contact the police again if he feels aggrieved, but that he won't be allowed home as he's risking social services being involved with your other son, and that can't happen. Social services will not be remotely interested in you kicking him out, he's too old now, they are literally hot air and no action, for any child over 13 (my friend begged SS for help with her 15 year old son and got none). It seems the situation has to be literally life threatening for SS to take action.
I get that you want your son to succeed in life, who doesn't? It's what loving, decent parents want for their kids, but sometimes you have to let that go and let them make their own mistakes. You have value too, and you deserve some peace, as does your partner and younger son.
My son has calmed down massively, is working and I see flashes of a decent human being shine though more and more, where as before I never saw anything decent in him. He's 19, the absolute worst times were 16-17.
Your son will grow up eventually, and hopefully realise what he put you through.
I'm sorry you're going through this, it's shit.