I'm not sure that going to the parents of a 19 year old was a good move. She's an adult. However, if anyone physically attacked me, I'd have called the police, filed a report, and applied for a restraining order to keep her away from your house and you and your other kids. You can still do that. But don't talk to the police about her texting - they don't care unless there are pictures of naked kids. They don't handle family discipline and drama. Focus - it's on the physical attack and the fact that your minor daughter is home alone.
You are responsible for your son's upbringing, but sometimes kids take a bad turn and we can't do anything about it once they are adults. We can, however, stop enabling them. I think you have to prioritize. What they do behind your back is annoying but you have to ignore it. If you didn't snoop at the messages, you wouldn't know about it. Kids who text constantly are annoying but it's not the end of the world. Same with dirty underwear on the floor of the bathroom - shut the door and let the kids work it out. You're not home so you can't micromanage everything.
Lying naked in your home when your daughter is there is another thin, but if she's in his room, your daughter can shut the door. So is leaving dirty stuff around. And stop asking her why she is yelling at your other son. Who cares? Just kick her out. There are precious few valid reasons for being a guest in someone's house and yelling at them.
But your son is allowing this when you are not home. And apparently he expects to be spoiled with a fancy car, an unlimited food budget and an expense account. So he's your problem. Stop paying for everything.Give him an ultimatum - he needs a job in 2 weeks or you're not paying his cell phone and spending money. If you and his dad want to pay for his college, that's up to you, but none of this "don't work and just concentrate on your studies" nonsense. If he has time for all this stuff with her, he has time to work. A job at the college might cover part of his tuition too instead of gas for his BMW. Give him a set time limit to move out too - a dorm, a rooming house, anything near the college. If they go to the same school, they can live together and pay for it themselves. But he's out. He thinks he's an adult and can do what he wants? He's right. But not in your house.
I agree you can (and should) change the locks once he's out. But if you let him in the home and then travel with your daughter, he'll let her in.
Time for tough love, Mama. You've either taught him life skills, or you haven't. He can learn the hard way, but at least he'll learn. But you have to stop all the talking, all the asking for explanations, and all the snooping. You have to take concrete action that he will understand. It's time to be strong and be in the driver's seat. We had to do this with one of my husband's daughters to keep her and her criminal boyfriend away from our son. If she wanted to see us, we met in a very public place like a restaurant that would call the cops if he showed up without our knowledge. We told her we would see her, and only her.
Good luck.