Sounds like you’ve done what a zillion other parents have done and are doing and I understand your frustration that maturation hasn’t started, it is unlucky but the boat you are in.
He has a good thing going, probably doesn’t believe you will pull the plug and really has no incentive to change what works for him. I agree with the others that it is time for a frank conversation (in person), with obtainable goals and expectations he has a chance of meeting. As you determine your limits beforehand, you have to have consequences you can live with too. I don’t believe you are ready to send him to the streets and having him back at home would be a punishment for you too, I suspect.
I don’t think it is fair to pull him or cut him off without warning. It doesn’t seem realistic to expect he will have a magical awakening. I’d be aiming for baby steps. If the first one is grades, his job should be studying and improving. He’s probably already in a hole this semester, you should understand where he is currently when setting your expectation for where he needs to be to satisfy you.
If he had gone from being very supported/ridden/managed in high school, to be able to do it all himself in college through osmosis, you would have been very fortunate. Since that isn’t the case, I would back up the bus and help him figure out how to get support to be more successful. This assumes that he buys in to your condition that he do better to be able to stay. Perhaps finding a tutor was overwhelming to him. (If you helped him identify a few sources, and he lied/blew it off, that would be another story.) Regardless, give him a fresh start if he wants one. Does he know how to study? I like the suggestion of finding a life coach/counselor to help him find his way.
I don’t think our job as parents ends at 18, and just getting kid to college is our finish line. They are chronologically adults, but more babied than our generation (our doing) so in many ways less mature. Some need time, some need a re-start, some need scaffolding to be removed gradually. No judgement here, just wishing you success getting your frustrating and challenging one launched.