I'm glad that he is willing to see a doctor. He will need to agree to have you come in and talk so maybe you can work that out with him in advance. If he has more suicidal thoughts you may want to get him to an ER so that he can get more immediate, appropriate help. I think that is probably very important to keep him safe as he sounds impulsive. A hospital admission may also get answers faster and also get treatment started faster.

I hope that you get some answers soon.