Thanks for bringing your question to JustAnswer.
This behavior would be understandable and acceptable if your son were 5 years old, but at 25, it's not acceptable.
While it's always hard for kids to think of their parents as adults with their own needs, that doesn't mean he has the right to run your home.
It's time for you to take back control of your life. If he can't behave in a respectful way toward you and your boyfriend, then it's time to him to move out. At 25, he needs to learn how to make his own way in the world. If finances prevent this, then it's time for him to move in with his father.
If he learns that he can get away with this behavior, you'll lose this bf and anyone else you try to date. He's being manipulative and acting like a spoiled brat--this man bought him a car, and he's still being rude. That's just not right. You aren't doing him any favors by letting this continue. Tell him he needs to make other living arrangements, or you'll end up alone after he's ruined your relationships.