wow, you have a very resourceful child. our recommendation here is to reiterate the rules with your child and make sure the discussion is around why having safe family installed will make his online experience better.
this is one of those scenarios that is falls outside our ability to do much. it would be like if your child picked up their friends phone and browsed the internet from there. you can check for your child's activity and if suddenly it stops then you know he's likely going into safe mode to bypass any monitoring.
hope that helps,