If the primary issue was delusions and not hallucinations that could open up more possibilities maybe.

I have read a lot about Schizoid Personality Disorder and as far as I know it's not associated with delusions in a meaningful way. Do you have the other Schizoid traits like blunted/flat affect, difficulty and low desire in regards to connecting with others, low motivation, prefer being alone, feel very little pleasure from anything, etc?

Schizotypal PD is more prone to magical thinking, outlandish ideas and paranoid thinking than Schizoid... it is definitely Schizoid PD and not Schizotypal PD that he diagnosed you with? Sorry if that sounds rude, I'm not accusing you of being wrong - it's just that people mix them up all the time and delusions seem much more relatable to Schizotypal... Schizoids are more know for being super-logical.

Even if it was schizophrenia I don't think it gets worse over time if you stay on meds but I could be wrong. There is a lot of good information online, wikipedia is a good place to start.

Atypical anitpsychotics are used to treat Schizoid PD, but it's only to help with the negative symptoms of flat affect, anhedonia, etc. since delusions are not part of schizoid PD. I also understand that schizophrenia usually has bizarre delusions. From wikipedia:

Bizarre delusion: A delusion that is very strange and completely implausible; an example of a bizarre delusion would be that aliens have removed the reporting person's brain.
Non-bizarre delusion: A delusion that, though false, is at least possible, e.g., the affected person mistakenly believes that he is under constant police surveillance.

Someone with schizophrenia would be more likely to have very outlandish delusions involving aliens, secret societies, evil robots, thinking they are Abraham Lincoln, etc. Paranoid ideas that are at least conceivable like someone trying to poison you or friends/family/coworkers conspiring against you would not be as much of a concern for being schizophrenic I think.

Next time you go to see him consider writing something out beforehand to let him read. Reading a few pages will only take him like 3 minutes - it's more effective for me because I am not very articulate at explaining things on the spot.