To say if my 17yo drops out of college he'll have to move out?

Why not send him to live with his father anyway? Frame it as it being so they each get to enjoy the pleasure of each others company.
With him almost being an adult you don't need any communication with his father, so he no longer gets to undermine you. Just refer any queries he has, to your son.

If he’s not academic and interested in studying then leaving college might save everyone’s time in the long run. I don’t think apprenticeships are that easy to get though and not something you can casually enter because you can’t be arsed with other subjects. My friends son is doing plumbing and he’s really had to hustle to find an apprenticeship and he was doing really well on his course and had lots of labouring experience and contacts. There aren’t tons of employers out there willing to employ a layabout because his mum wants him to have a job

I’d probably rein the emotional stuff in ( difficult because he doesn’t care about your feelings clearly). Remain super calm. This is his path to walk and he can walk himself right out the door to his dads.

Are you funding his weed and alcohol purchases? If not, where does he get the money from, dealing?
It's a red flag that he has treated his GF badly, could be the weed
I would make him leave at 18 if he didn't shape up.

Definitely say you'll cut off his allowance and stop paying for phone etc.

The fact is if he does quit college it's unlikely he'll suddenly develop the kind of get up and go that would be required to come across as a responsible employee.

There are thousands of very responsible student age kids who want to work and obviously they'll be on top of the list when it comes to jobs.

If you tell him he needs to move out then you need to be prepared to follow through on thatm I feel really sorry for you.

This would be my approach too, but it can only work if his dad agrees not to give him money as well.

Looking into apprenticeships might also be a good option if work would suit him better than college.

I really feel for you. I found this age also really difficult. Like your son, mine left school with barely any qualifications, went to college but didn’t apply himself at all and ended up leaving. He was up to all sorts and it was an era of parenting I found especially hard.
I picked my battles and had to overlook an awful lot. The one non negotiable was he had to either be at college or working. Once he left college we did not subside him at all except for food and housing. If he was at college we supported him financially but once he left that was it. No money for phone, Netflix, socialising, clothes etc. Anythibg he wanted he had to earn and he did. I would say unless you will definitely follow through with the move out threat it is just hollow and he will know that. Realistically unless he goes to his dad (which doesn’t sound ideal either) there is no where for a 17 year old to move out to.
For what it’s worth my son is now 24 and a lovely man. He returned to education and is currently at uni. Hang in there and try and focus more on yourself and just getting through.

You can only do so much - dragging a horse to water and all that. You have made your position clear. If he drops out, he either gets a job immediately or moves out because you will not tolerate him lying around all day doing nothing. Fair enough.

I have a friend who had this exact same issue with her son. When he tested her by dropping out, she packed all his stuff into bin bags and dropped him round at his father's house, then changed the locks.

It took him 5 years to sort his shit out and with hindsight I was very impressed with her resolve. She wouldn't have been doing him any favours if she hadn't followed through with the clear consequence.

Could you phrase it more as 'if you drop out of college you must have a back up plan in the form of a job'.

I can't imagine how hard it must be and my heart goes out to you. Unfortunately I think you're on the right lines with telling him its a job or move out if he leaves college. He probably doesn't think you're serious. Show him that you are. Take away any money for extras that you may be giving him and advise on how much notice you will give if he does not look for work. You have to draw boundaries now. So many youth today seem to be like this and its not your fault, something is badly wrong with society now.

Has he considered that he will have no income at all if he does this as the child benefit stops and of course you won't be giving him money. He won't be able to claim UC as living with family. If he leaves he is in danger of joining the ranks of dysfunctional youth who become increasingly unemployable and are generally homeless or sofa surfing. Could you suggest he finds an apprenticeship and then leaves college. What is the reason he doesn't like college? It's too easy now for them to spend all night gaming and sleeping all day so if this is thing, turn off the WiFi at night.

Where is he getting the money for weed and drinking if he doesn't have a job? Put a stop to that shit, right now. Stop paying for his phone, stop paying for everything. All you have to do is provide shelter, food, water and sanitation.

He'll soon feel the pressing need to get a job when he can't afford to do anything.

YANBU at all its like banging your head against a bloody brick wall when it gets to this point.

Can you stop paying for any extras now? Phone? Treats? Though I know that can make things worse for you when it's already bloody impossible.

hugs