My doctor said it is okay to come off my psychiatric medications. How do I go about doing that? I bought a scale that measures in mg thinking I could start shaving a little off of them slowly over time.

You should be working with his doctor and pharmacist to come off his medication. But most likely, they will tell him to come off too quickly. So just make sure you go very slowly. 

The main supplement that helped me the most when coming off my psychiatric medications was DL-Phenylalanine. It's an amino acid supplement, and it has helped a lot of my clients as well. It seems to reduce withdrawal effects. It's also known to reduce pain too. You could try taking that and see how you reacts to it.