Hello. I am so sorry to hear of your pain, as well as your son's. Our son is 25 years old also and we have been to hell and back since he was 19. I highly recommend NAMI. There are 8-13 week long educational programs (depends on the chapter) as well as weekly family support meetings. Please look up in your area and see if you can attend in person and/or by Zoom. If you don't feel comfortable with your local chapter, there are many others throughout the country. I have gone through the training as well as weekly support meetings, both of which were immense help. In regards to suicidal comments, it is my personal opinion (others may have their own opinions and professionals and interventionists their own as well), that you do need to listen and take each one seriously, even if you think he is manipulating. You can urge him to call 988. NAMI will train you how to deal with those calls. I have found that sometimes I just needed to block my son at times when the calls were incessant. Even if it was just for several hours. If you think he is suicidal, call 911 or check with NAMI to see if there is a response team in your area. If he is a threat to himself, others, or expressing suicidal ideation, you can see if you can get "white papers" in your state. However, and most unfortunately, this can be very difficult to do.
If you can convince him to see another therapist or psychiatrist, remember that you can always share information with that professional even though they won't share information with you unless there is a signed HIPPA on file. And if the calls are incessant and he refuses to seek help, you can say "we love you but want to see you get help". As many times as it takes. I had to learn how to "validate" his feelings. A good book is "I'm Not Sick I Don't Need Help" by Dr. Amidor which can train you how to talk with someone who lacks insight into their mental health issues. And someone suffering from bipolar disorder can suffer from lack of insight. And remember self-care for yourself. My best wishes to you.