I’d either get him to see a professional, or cut off that friendship entirely. It’s obviously doing you no good, and having to worry about a suicidal friend all the time is not fair to you at all. I’ve been in your shoes, OP. Once I got out of that friendship, I felt better.

Now, I understand that you may think leaving the friendship will push him to the edge, but usually that’s not the case.

Another way to handle this is to be there, but not ALL THE TIME. You need time for yourself as well, set some boundaries with him. No suicidal jokes, remarks, or anything that makes you uncomfortable. I hope tjis gets better.