Hey, Grandmamma.
I am so sorry about your son-in-law and I understand. Do you know that sleep deprivation is a form of torture in many countries? That's because people will say or do just about anything just to get some sleep. It can truly make you think you are going crazy and I can imagine, in enough pain to just want it to stop. If you go long enough without significant sleep, your mind will grab even seconds of REM sleep here and there and it feels like hallucinations.
I am NOT a doctor, just someone who has a sleep disorder and has been there. He needs immediate help for his depression and suicidal ideation. I would really try to convince him to get to see a psychiatrist who can recommend a neurologist who is a sleep specialist and get him a sleep study.
He probably has a treatable problem even if it doesn't feel that way to him now.
He definitely needs help, even if someone has to drag him there. EMS in most communities have mental health workers.