Hello, OP.
I feel your pain, I hear your pain, and I've probably experienced something very like it, still am in the middle of it. So sorry if this post is long.
I think it is normal for a some teens to want to get away from home, so I wouldn't take much notice of that. I also think its fairly normal for some teens not to want to join in conversation with parents. So I think there you are doing the right thing to back off really.
But the abuse? Nah. Verbally abused daily? Disgusting, entitled, brattish behaviour. I know some teens have a hard time adjusting in life, and lots of teens have "phases", but that really is no excuse for long-term nasty and abusive behaviour to their parents, especially their single mother. Its completely unacceptable.
Talking to him isn't an option I've tried the hard approach, the soft approach, Internet ban....... everything
What can you do about it? Well yes .... here comes the tricky part. Like you, I've tried everything: talks, contracts, understanding, reasoning, distancing, disengaging, everything. Whatever it is it works for an hour or two or a day or two (if I'm lucky). But the end of the day though I have a similar boy DS16 who is fine and apple pie until even the simplest demand is made on him, and then its irritation, rudeness and explosion. I've read all the books, Explosive Child, yada yada, I've researched possibilities endlessly, and its led me just further down the road of walking on eggshells and being treated like shit in my own home.
My latest decision is: zero tolerance is the only response by/at this stage. Withdrawal of all privileges for any infraction on basic rules of home - including respect and basic chores. That means no phone, no internet (ring up mobile company and cancel sim or phone temporarily) until things improve. No pocket money. Remove again for any infraction. Rinse and repeat. If he's desperate to contact people he can buy his own PAYG, whatever, not your problem 
. I don't know what you will do about his "special interest" though. I suppose you could continue to chauffere him there, or not, up to you. For me, none of this is meant as a "punishment" btw, I'm even past caring now if he changes his ways or not. I'm just not giving him any privileges when he's being so nasty. Why should I?
You are bound (legally) except usually in exceptional circumstances e.g. actual violence), need to house him, buy him food and keep him healthy till his 18th birthday, but after that, if his behaviour is still going on you can tell him to leave, and in fact prepare him well in advance for the day. He sounds bright and together in other ways so he should have no problem in looking out for himself and getting his life together. Like you I've put up with his shit for close to 3 years now, and its killing me. I deserve some peace and a break - and the way I look at it its just over a year off ...
Anyway, this is my latest approach. I don't know if it will improve things, probably not, I feel we are stuck in this for another year.
Anyway, I'm now going to try and have a lovely bath.
I'll cook something nice later and have half a bottle of wine.
For now, I'll try and repair my heavy heart - after our last almighty row - by doing good things generally and keeping going.
I'm making plans (in my head) to try and do some good things when I can over the next year and even further year down the line when he's gone and I'm free.
to you OP, you are not alone x