I did my A levels in late teens and early twenties after leaving school at 16. I worked while doing them, because I was too old to live at home and not contribute. I got good enough results to get into Cambridge, where I read law.
Your son may find he does well in his work, and loves it, but why in the world does he imagine his chances of university are now over at the tender age of 18? What's to stop him doing A levels part time, as well as an apprenticeship, or when it's done and he's qualified? He could even find an employer would sponsor him through, so he'd have far less debt.
One of my younger half brothers dropped out of an accounting degree because he hated it, and only did it to please our father. He then did an electricians apprenticeship, and did well. Was earning good money. He decided, in his mid 20s, that he would go back to university to study engineering, because amazing money at 25 isn't at 45, and his progression in salary terms was limited. Since going to university he's pulled in amazing results, because years in the workplace instilled an incredibly improved work ethic. It was the making of him.
I also suspect he wants to go to university because he sees it as years of partying, in which case he'll end up with a poor degree, a mountain of debt, and without improved prospects. The electrical engineering apprenticeship sounds brilliant.
Your son is at the very start of his life. He has years ahead for university, if that's what he wants to do, and this apprenticeship, if he takes it seriously, can only smooth his path.
I'd let him resent you (though not treat you badly). That's what parents are for, at his age. I do think the job was a bad idea at that stage, and some kids do pull amazing results off last minute, but he was not behaving well either, and to shuffle all the blame on you is awfully convenient. But he's only 18. Surly adolescents are the norm, I think. It will pass.