Please Help I Can’t take it anymore 😫

So I have temp custody of my husbands little cousins one is almost 2 the other one is 4 and the oldest is 11. So I stay at home and take care of the kids including my 11 month old, while he works 12hr shifts. Ok so the 4 year old is extremely mouthy, for an example I would ask him to put his chair back where it belongs when he’s finished with it. He looks me dead in the face and says I will put it where I want and you will deal with it. And another one i couldn’t afford to buy chocolate milk because I had to buy stuff for dinner, (I have to budget my money more with taking in 3 more kids) anyway we get going down the road and he’s mad at this point he unbuckles his seat belt and gets in my face while I’m driving and starts screaming sayin I said get my chocolate milk now. Trust me he did get in trouble for this. He’s also been bullying at school which I absolutely do not tolerate. I’ve tried everything to get him to listen, I’ve taken conscious discipline classes, I’ve tried time outs, I’ve tried busting his ass, I’ve tried literally everything and nothing is working. I’ve also tried this with the almost two year old, he will scream nonstop on purpose all day long, I’ve tried babying him, and trying to explain that we don’t scream, I told him he will get time outs and I’ve put him in time outs and still nothing. He’s also very very mean to my baby, he shoves her in the toy box, breaks her toys, calls her a bitch, scratches, pinched and bites her. He’s even grabbed her by the throat while I was cooking and slung her across my living room. There’s nothing I can do to make these kids stop. I want a break and I know it sounds selfish but I’m ready for these kids to go back to their mother. My poor daughter is so scared of them, she won’t play with her toys because they always take them and break them. All I can say is I tried and I’m ready to give up completely. Someone anyone please give me advice, please tell me I’m not the only one? I’m sorry for this post to be so long.