Change in meltdown behaviours - Self harm, suicidal ideation and violence

Hey everyone.

I'm looking for advice, but also kinda looking to see if anyone has had a similar experiences to what I'm currently experiencing at home.

My son 11 (ASD/ADHD) is a wonderful loving and affectionate boy. I actually found his ASD (though severe) easy enough to manage by watching for escalation and triggers and using the "hugging" technique to suppress his sympathetic nervous system before he could go off. The only time I really needed to be careful were during times of "Flashback" where he'd remember something from days, weeks, months or even years before that had no trigger warning signs. But these incidents were few and far between.

His major trigger is self perceived failure. If he thinks or feels he has failed at something he goes up like a roman candle.

Recently his self harm has escalated, he's started trying to seriously injure himself. -Attacking himself with scissors in school, trying to throw himself off a balcony at school, trying to shove a fork in a plug socket at home.- He's made comments or statements along the lines of "No longer wanting to live anymore." He's also started becoming a bit violent. (He's always lashed out during meltdown but) this has recently developed into him catching me off guard by raising his fist to my face which causes me to jump back from him. He does drop his fist when he sees this and then cries because of my reaction of fear. The problem that I have is his flashbacks are increasing he's lost his visible escalation process. Even his school (who are SEN resource based specialists) have stated that of all the ASD kids they have they've never seen a child who instantly hits crisis without warning.

My son is like Jekyll and Hyde whenever he's having a meltdown and all my former calming techniques that worked so well previously now only seem to escalate him further.

I tried talking to my son's specialist at CAHMS about this as both myself and the school are incredibly concerned. But she simply shrugged her shoulders and said "This sounds like Autism meltdowns, nothing to do with his ADHD" - Which felt like she was basically saying "Not my problem, not my specialty"

I am simply at a loss of coping right now. I am a single mum and my older daughter (13) also has Autism with severe social anxiety and I feel like all my energy is going into my son and it's exhausting. Further frustrating is the fact that the school are absolutely concerned but not as concerned as they are about his attendance. Which ass backwards to me. Shouldn't their main priority be his health and well-being? I cannot physically drag my son to school when he's being violent or having a meltdown and sometimes when he's voiced the desire to die or tried to hurt himself I'm staying awake for days on end so I can make sure he's not hurting himself which then exhausts me too much to get him to his taxi drop off point in the morning.

I'm honestly at my wits end.