How can I stop arguing with my dad?

Alright, first off: I have to give you the entire story before I ask the question.

I am 18yrs old with no education and no job. I’ve been homeschooled since I was in first grade but it didn’t exactly work out as you may see. I’m thinking about going to Job Corps to better myself and I don’t have any support from my dad. I’ve been taking care of my autistic brother for over eight years and now, I’m ready to start get things going for myself but he said to wait and have patience, and see what happens. I’m tired of waiting and I’m tired of him telling me what I can and cannot do with my life. He says that my path doesn’t lie with college, it’s not where I’m destined to be and - I’m a child who doesn’t know anything.

I can’t undo what happened in my past but I can fix what is going to happen to my future. And he won’t let me to be honest. Basically, I’m a sibling raising a sibling. My parents are going to put my brother in a program for kids like him when we go back to another state but right now, I have to wait. Sure, I can do that but my point is, when I get back to where we’re going, I’m not going to watch my brother constantly like he is my own child. I should be out in the world, learning my own way in life, I’m too young to be taking care of a child, you know? I’ve told my dad how I felt but he told me that family comes first and I’m being selfish and Job Corps for losers. And he tells me that I need to be responsible for my own brother. I’m like: What the heck? What about you? You’re the father! He’s like: We share it. I’m like: You don’t do anything. Act and be a father to your son. I got in trouble for that one. My parents are seperating and I’m going with my mom who supports me in everything I do unlike my dad who says everything I do is wrong(the things that he agrees with are the things that he wants). And my parents argue no less in front of me. The thing is with me… I can’t keep my mouth shut when I hear something they are talking about and when my dad does things I don’t like… I can’t keep my mouth shut about that either. My question is how do I keep my mouth shut and how do I handle my situation with my dad? Running away isn’t an option, it’s stupid. But how do I tell my parents - nice and calmly - that I’m not waiting anymore and that I have to go to Job Corps when we get to back? Like a week or so later when we arrive there? Please, I’m desperate and I need your help. Sure, I’m 18 but I have no job nor education like I’ve said.

Please help.