Sorry, but you are being totally ridiculous with those rules. He is 16, not 10 or 12!
I have a 19yo and a 17yo (turned 17 on Christmas Eve). We don't have rows, we never have because they are not controlled by ridiculous rules.
If they make their bed then it's fine. If they don't, I pull the door to and walk past it. They have to sleep in it, not me.
Internet is free range in this house. DS2 is often doing his homework or revision until 9pm. No way am I turning it off then, he needs to have some down time and relaxation. 10pm on a weekend, never in a million years. You do realise he will be coming in at 4am when he is 18, don't you?
Baths or showers, what does tj matter? Be grateful he is having them, so many teens don't. It would not occur to me to dictate to someone with an adult body how to keep it clean.
Turning lights off is infuriating, but not worth chucking your child out over.
Mess and chores is something that goes with the territory of having a child, especially a teenager.
You sign up to be a parent for life, for all of it, not just the nice bits. Stop shouting and talk to each other. I feel really sorry for him. He's been at boarding school and now he isn't wanted at home, poor boy.