1) as long as he pays the bill for the internet service, he is technically your provider and can do, on his machines, whatever he wants. If you complain too loud, he may realize that he doesn't have to let you use his internet service.
2) by getting your own internet service. As for accessing your laptop, that's going to be a bit more difficult on your part. You'll have to use disk encryption with a strong password to keep him for accessing your data when he has physical access to your machine. Legally - well, you may sue and you may win. But then again, as you're apparently living with your parents, that may also change very rapidly in this case, whether you want it or not. Your life, your decisions, your consequences. Simply moving out would be the easiest and, in the long run, cheapest option if you can't find an arrangement with your parents.