I guess I am much firmer with children than you are
Personally I would not let your Son access his or your computer unless you are able to monitor him. Is it a Laptop or PC. If Laptop take it with you when you leave the home. If a PC, put a lock on the door where it is kept. I would show him who is boss to be honest. What punishment have you in mind for him hacking into your settings.
Using K9 would be no different to taking the computer away so he cannot use it unless it suits you. He will thank you in the end with more respect if you are firm with this issue. May take time, but he will thank you as he gets older.
Can you also suggest other activities outside the home to interest him. Join him up to a club of interest, perhaps a sports club, book club, or whatever would interest him.
I have to say if my child hacked into my parental controls it would be the last time he used any computer in my home.