Not posted on here before, so will give a bit of background first.
I have been separated for 2 months, and the few months before that where not great.
DS2 is the eldest child with my ex, ds1 from previous relationship and doesn't live at home.
DS2 has ADHD and has always been a hand full, DS3 has severe Autism and learning difficulties, so I am sure you can imagine I have quite a difficult time as it is as I have very little outside support.
STBXH has moved in the his DF's house with FIL and BIL, they are both heavy drinkers and BIL is a drug taker, so no chance of any overnight access or even anything longer than an hour or so. EX doesn't seem to get the difference between seeing the boy and spending time with them so just calls round for half an hour a day to see them and goes home 
DS2 has been a nightmare lately. His paed has upped his meds but we are still having a bad time, I don't think his behaviour is down to his ADHD.
I completely lost it this morning. He has been refusing to go to bed at a reasonable time and last night I heard him get up at 2am, he went downstairs making loads of noise in the kitchen. I got up and found him filling ds3's sports beaker with water, he had a load of food out ready to take to bed with him. I told him he wasn't taking any food up and if he wanted a drink of water to use his own bottles (I have bought 2 sports bottles for him to use at night). He started shouting that he would do what he wanted and he was taking the food because he wanted it. I finally got him to go to bed without it and use his own bottle.
All this woke ds3 up who stayed awake till 6.30am, which is when I finally got to go to sleep 
I was woken up at 11am by ds2 shouting at the top of his voice at his Xbox. When I got up I discovered he had been up for some time and had eaten half loaf of bread, well when I say eaten he had toasted it had a few slices and just left the rest. He had destroyed the kitchen in the process and drank all of the milk, a whole litre. He had also trashed the living room.
I lost it! I got hold of his arm and pulled him around shouting at him about what he had done.
The problem is he is doing this on a daily basis. His attitude stinks, the way he speaks to me and the language he uses is disgusting.
I have speaking to ex about it and all I get is 'you are the parent, just sort it out' or 'I will have a word' then I get a lecture about how I shouldn't let him get away with it.
I am at the end of my tether with it. I am totally exhausted as even on a good night I only manage to get about 5 hours sleep as he is refusing point blank to go to bed and short of dragging him there, what can I do? When ever I try to get very strict with him he will start screaming and shouting.