Welcome hopenlove: He has started using cutting and suicide threats as a way of dealing with his emotional pain. He refuses to contemplate any form of therapy (he did dbt for 12mths but never really practiced he skills or did homework and ended up getting kicked out) so he has a bad view of dbt and group therapy based on that experience. My main concern is that he keeps saying he "wants to die" and argues the various reasons, very persuasively, why he shouldn't be in this world.
I'm so sorry for both you and your son. It has to break your heart to see him like this and not be able to help. I've listed some resource links for you.
The Safety First link will help you with a Safety Plan. You have to take your son's threats seriously and having a plan mapped out can help in a crisis.
SAFETY FIRSTSUICIDE IDEATION IN OTHERSThe group of resources below can be both beneficial to you and for your son. The first two Resources are for the US and the third one is for International Resources. It would be a good idea for your son to have the numbers handy in his phone, so he can reach out to talk to someone. The same thing would apply to you. Suicide prevention services are there to help distressed family members as well.
SUICIDE PREVENTIONTEXT CRISIS LINEINTERNATIONAL SUICIDE RESOURCESThe two resources below can offer some helpful information and possible strategy to consider using.
What to do when feeling manipulated by suicide threatsSUICIDE IDEATION IN OTHERSThese two links go to a DBT Self-Help Website. The information could be helpful for your son. Perhaps you could even print out some of the information for your son to use.
IMPROVE THE MOMENT WORKSHEETwww.dbtselfhelp.com/html/improve_the_moment_worksheet.htmlPANIC LISTwww.dbtselfhelp.com/html/panic_list.htmlI hope some of this helps. Keep us posted on how things are going.