Sorry man, I had a reply typed up but it vanished when BL crashed for a moment.
In short, I'm fairly sure his prognosis is good if he stops using drugs (all drugs, not just meth) and receives active treatment - the sooner the better for both. I don't remember the numbers, but most meth users who experience psychosis recover fully if they stop using meth and receive treatment.
He should either contact his doctor, be open about his symptoms and drug use and ask for a referral to a psychiatrist or, especially if he doesn't have a good relationship with a GP, he might have better luck getting a referral to a psychiatrist with experience treating the side effects of meth use by going to his state Drug and Alcohol service. Can't hurt to at least give them a call. He needs therapy, an evaluation to see whether he needs to take anti-psychotic medication for a little while and, I can't stress this enough, to stop using drugs. Most drugs will aggravate the psychosis in one way or another.