My dog doesn't like training or discipline. He wants freedom and is aggressive!!

I need help! I currently own a 7 month pitbull/mastiff mix named Zulu. My boyfriend and I have been training my pup since he was a month old and for an energetic pup that wants his own way, he has done very well. So here’s the problem. My boyfriend is trying to save money for when he goes to law school next year and I’m currently looking for a job so we are both staying at his parents house. My boyfriends dad, as well as his sister who visits, allow Zulu to do as he pleases. They don’t enforce our training. We give Zulu commands to do when he wants something. Sit, lay down, speak, and wait. Before we feed him, give him water, take him out, or give him a toy he must do these things. He’s not allowed on the couch and is he does something wrong or bad we put him in the downstairs crate for 30 minutes or more until he calms down because we know he likes to be out when people are home (best punishment in our minds). But with them they don’t do any of the things we tell them, even if he gets sick and the vet tells us something specific to do, his dad doesn’t do it. If Zulu is misbehaving and is in time out, his dad will come home and let him out to go crazy. Zulu knows he can get away with stuff with them because he never listens to them, just my boyfriend and me. Because Zulu knows he can get away with whatever when they are around he is starting to act out. It has gotten so bad that when he knows his dad his home he’ll become aggressive with me, barking, growling and now even bites. He’ll do this then when I put him in the kennel he’ll whine until his dad rescues him. Usually he’s fine when we are alone but now he’s even become aggressive when it’s just the two of us. I can’t even take him out to pee or use the bathroom without him growling at me, I guess he knows I won’t let him do as he pleases and he wants no parts of it. His dad doesn’t listen to anything even now knowing he’s becoming aggressive. We can’t properly train and deal with his aggressiveness in this house but we don’t have the money to move out so for now the only option is to stay and put up with the back and forth training or to get rid of Zulu, I don’t want to do either. Since his dad won’t listen I want to know how to deal and correct his aggressive behavior. I know hitting a dog isn’t the best when a dog is aggressive or defensive because it makes it worse but it’s hard when I’m trying to defend myself from his bites. Even when I don’t swat at him and I just try to push him back in his crate he’ll still try to bite and lung at me. I don’t know what to do and it’s really frustrating because I’m the only one he bites. He growls at my boyfriend because he also doesn’t give him the freedom he wants, but my boyfriend can tell his dad about himself and he somewhat listens after so Zulu knows if he bites my boyfriend he’ll be in deep trouble. I don’t want to get rid of him but there’s no telling how long I’ll be here and his dad will never change, I know because he treats his grand kids the same way. What do I do??!