Sons gf took her life tragically in February, now my son is at risk of taking his

Hello, my son, 27 yrs old, type 1 diabetic since 9 already suffers from PTSD from his early diagnosis and his father’s drug addiction. Unstable blood sugars mean unstable moods most times, or depressive tendencies I guess is more accurate.
He recently was at the top of his life finally. He landed a high paying job, and was promoted 4 times in one year boosting his self esteem. He was in therapy finally, and healing from past traumas. He was on medication for depression and I for the first time in a long time heard excitement for life in his voice. It was beautiful, and also makes this harder.
Late February his girlfriend of several years took her life in a very tragic way. They had fought the day before, sadly the fight went like this - she told him “I haven’t been happy with you for a long time.” So he said if she wasn’t happy she could go, she wasn’t being forced to be with him. So she left and took her life. then her parents and all her friends sent him hate messages blaming him for her death.
my son did so much to help her. She had been hospitalized 4 times in 2 years for suicidal ideation. My son got help for himself and encouraged her to also get help. Asking her repeatedly to see a therapist. He also took a month off work just before her death to care for her in her depressive state and to make her happy. He is taking this blame personally. it doesn’t help that less than 4 months later, and on his birthday, his father also dies.
my son who was trying so hard broke, loosing his job, his home, all his contents he couldn’t pack in his truck. he moved to Colorado to be closer to his dads side of the family, but most of them are high all the time and not a good support.
my son has in the last several weeks been showing many signs of the end for him. Closing down social media, isolation from friends and family. And now he’s moving out of his brothers to live in his truck. I beg him to come here to Alabama to stay with me until he can get his bearings, but he refuses. I flew to his side when his girlfriend died, and again when his father died, then again last month. I don’t know if I should make another trip, but I can’t afford to really go, or to go once a month. But I would do anything if I knew it would spare my son. I’m so overwhelmed with worry, I cry nearly everyday, and sleeping is difficult. Sorry so long, I promised myself I would keep it short, but here it is. Thanks for reading