Ok so from the sound of it your still pretty young as your talking about supervision and whatnot. I understand how you feel about moving into a supervised environment, that really sucks.

You said "if he finds out there's thc in my blood test he'll call the cops on me" and that seems to be your only concern with being clean. I just wanted to let you know it not illegal to fail a drug test, there is a huge chance the cops wouldn't even come discuss it with you or you dad and in any circumstance ( unless your dad hides a dime on you ) you couldn't be arrested.

Even straight up saying "that guys has weed" to the cops in most places won't warrant any action or repercussion.