Dill, nobody uses crack cocaine for 8 months then gets found out and just decides to stop cold turkey, no problems, tralala. Nobody.
And if he did, he would be bending over backwards to prove to you that he was never going to do it again, not hiding out in his shed, disappearing for days on end, ringing his dealer at 3am, getting angry with you and organising overdrafts despite a big income.
Colditz is absolutely right, this guy is clearly using, and he's putting you and your family in huge danger because of it.
He's acting cross with you, and lying to you, because he's scared shitless. He's addicted to a Class A drug. He knows that you'll kick him out if you know that he's using, but he can't stop and he hates himself for it but he can't ask for help because that would mean admitting that he's an addict, and that he's been lying to you. So he's in a loop of addiction and deceit and despair, and he doesn't know how to get out of it.
While he's prepared to lie, and you're prepared to pretend to believe him, there is NOBODY helping him. You are not helping him, you're propping up this increasingly thin charade. He can't help himself. There is NOBODY for him, and he badly, badly needs help.
The only way you can help is to insist he leaves, undergoes rehab, and comes to counselling with you. Tell him you love him, but you can't live with an addict, and he's an addict, make no mistake. He has to leave either way. What he does from there is his choice; rehab and counselling, or he stays away. But you need to force him to face up to the fact that he needs help and he will lose his entire life if he doesn't admit that now. Sweeping this under the carpet isn't helping anyone. It's risking everything.