I'm in a similar position as Stee. I've really never heard and don't think there's any solid evidence to suggest that Baclofen would be an effective treatment for Amphetamine Psychosis. That doesn't mean it won't have any effect on your situation at all, of course it will, but will these effects be significant and positive enough to warrant the drugs future use for this purpose, I don't think so. Baclofen is similar in some ways to the Gabapentinoids, but in my opinion it's not nearly as useful as said drugs.
The best drugs for reducing Amphetamine Psychosis are probably going to be the antipsychotics. It's common to administer a Benzodiazepine followed by a drug like Chlorpromazine (Thorazine) or Haloperidol (Haldol). If you're by yourself and not looking to seek medical attention, then taking a dose of a Benzodiazepine would probably be helpful to get you to sleep, which is ultimately the factor contributing the most to your psychosis.