:hugs:Chloe, sorry you're having such a tough time. Don't be so hard on yourself, especially if your DH is working and isn't there to help you. You need a break too.
I don't have any experience with my own children having difficult behaviours and it being 24/7....yet, so I don't know how hard it truely is for you!! But being a childcare worker, I have had experience with most of the behaviours you have mentioned.
Does Yasin go to childcare? If he does, talk to the carers there, they could give you some insight to whether or not his behaviours are normal, but to me they do sound completely normal. And if he goes to childcare, you could have some time to yourself then too. Unfortunately it sounds like Yasin is very resilient and seems to ignore the negatives of the behaviuors, like getting into trouble, to seek the positives of getting your attention, and if you have to watch him all of the time then you can't giving much attention to Imran which could also be a pay off for him.
As for the toilet training have you tried a star chart or something similar? Sometimes something as simple as that can work wonders.
Do you think he could be bored? Sometimes when kids get bored they really try your patience. Do/can you ignore his behaviours? Tell him he's not going to get what he wants and when he's finished screaming you can talk.
That's all I can think of now. I don't know if any of it helps. I hope it does.