J.M.
I'm not a parent of a 15 year old, but I am a high school teacher, so I have now had experience with just about 600 15 year olds, if not more (wow, that makes me feel old).
Honestly, I think that the FU came about from a serious need to save face in front of his cousins. While it's not acceptable, it's totally understandable. I'd apologize to him for calling him out in front of his cousins, and I'd ask him to apologize to you for being rude. Sometimes the hardest thing that we can do is admit to our kids that we did something that hurt them, but I honestly believe doing that builds the best relationships.
I agree with many of the posters that the rule about only going out Friday and not Saturday seems a little arbitrary. Why did you put that rule in place? The 10.30 weekend curfew also seems pretty severe. Many kids would say that's like telling him that he can't go out at all, as he can't go to the late movie is friends will want to go to, or his friends will have to leave someplace early to get him home. Is it about keeping him safe? Make rules about drinking, or letting you know where he is, instead of just saying a certain time.
Also, the "politeness rule" is a tough one. 15 year old boys grunt. It's a fact of life. I mean, obviously please and thank you should be hammered in by now, but do you really want to battle over good morning and good night? He'll be out of the house so soon, and he'll grow out of this stage, why fight?
As for the phone, believe me, I totally get this battle. It's virtually impossible to get them to turn their phones off for a 55 minute class! Still, I think that the rule feels a little arbitrary. What is the point of the rule? Do you want him to finish his homework? Sleep through the night? Not spend a fortune on texting? Make rules that support him making good choices about those things, rather than simply saying 10pm. I like the idea that the phone stays in the kitchen while he's sleeping (a lot of my students wake to check texts in the middle of the night, and that's just not healthy). Also, you could give him a set amount of money for texts and above that he has to pay himself. As for homework, it sounds like he's a good student. If he continues to get good grades, his phone probably isn't a problem. If his grades drop, give him a specific GPA he has to reach for him to get his phone back.
The number one thing that I've learned as a teacher is that kids respect strict, as long as they feel that it's fair. They like to know what the rules are, why the rules are in place, and what the consequences are. As a teacher, I'm pretty tough, but my students always say that I'm fair, and that's more important. My guess is that your son feels like your rules are unfair - he's being "punished" for normal teenage behavior.
Good luck. I'm not looking forward to the teen years.