Suicidal and no longer coping with my son

I'm a single parent of a 6 1/2 year old boy with ASD and suspected PDA to boot. When he was diagnosed, we managed well. We were then discharged from the service and then from OT. Maybe about 10 months later and I was at the end of my tether and felt as if I no longer could cope. I phoned and self referred back to the sleep clinic (who were useless), and referred us back to the psychologist. It took another 11 months to get an appointment, at this point I am beyond exhausted. I am isolated. I am done. 

DS constantly pushes boundaries, refuses to do anything he's asked, has frequent meltdowns where he screams in my face and hits me while i have to sit there and try my best to remain calm. He actively seeks a negative reaction, which I try to ignore as much as is reasonable but he will persist until I have to intervene. He is messy, ungrateful, speaks to me like dirt - like demands I clean up his urine/faeces he has "accidentally" gotten on the carpet or w/e. This is one of the more extreme examples of course but it happens fairly often.

I follow a strict bedtime routine: dinner, bath, toilet and teeth, story and bed. I start all this around 5.30/6pm and finished around 7ish. His behaviour at bedtime is pretty bad. He will run through the house, refuse to cooperate, pee all over the bathroom, anything to get a rise while laughing his head off. Eventually when the bedtime routine is finished I have to sit in my room until he is asleep, if i go down the stairs then he follows, runs through the house, starts it up all over again. When he stays in his room he jumps off his furniture, the window(!) and will make excuses why he cant be in bed, laughing at me if I get stressed. It typically takes till around 10/11pm before he falls asleep, when he wakes in the morning for school he is exhausted, irritable and usually has a meltdown over something or another. 

I can't have friends over to my house, DS dominates the conversation, will not let me speak to my guests and if hes ignored then he will have a meltdown. My partner of 5 years moved in with us last summer and has just left me because he cannot cope in this house with my sons behaviour. I don't even blame him. It is completely miserable here. Regardless, my heart is completely broken and I am conflicted between feeling let down and missing him.

I am a student working towards qualifying in my dream career. Now, however, I don't think theres any point in me even trying. The childcare facilities in my area are basically non existent bar an after school club, there are no autism experienced or qualified childminders in my area either. The way things are right now, I can't see how I am going to manage 40 hours a week placement hours so what is the point? I don't want to spend my life devoted as just my sons carer and never achieving any of my own goals.

I have my own mental health problems too. I am experiencing a severe depression and I suffer from anxiety. I feel like I have no control over my life, I have no respite, my partners left me and I have to deal with all this alone now. I havent seen another adult since I went to college last wednesday. I have no friends anymore and I feel so trapped in this house as everytime we go out there is a meltdown and a drama no matter how much prep I put in. 

We don't have any support currently, we dont have a social worker although we are due to see the psychologist again after the summer. 

I don't know how I can keep this up. I don't want to be here anymore, I just want to die, I can't cope and I can't see how things will change. In a kind of cruel way, I know I can't commit suicide as my son completely relies on me and there is no one else. This adds to the feeling that I have no control over my life, every aspect is dictated by my son. 

I need help, advice, tips, kind words, anything. I'm desperate.