Sounds like progress. When he becomes less psychotic approach the guardian issue as a safeguard mechanism for his protection when he becomes psychotic again. Emphasize the benefits. Most guardians will also work with a person to allow as much autonomy as is feasible for their condition and honor their wishes and preferences when possible if it is in their best interests.

Delusions, especially religious ones and ones of persecution do not respond to reason but he can learn new behaviors when he is less psychotic and more amenable to suggestions. The progress and extra help should reduce your stress and make his life better too. I hope things continue to get better for both of you.