Well done giving up smoking pot.
Is not telling your parents helping you? Think how much the burden of guilt is costing you and draining the energy and inspiration you have to claiming the life you are stepping towards? I've screwed up and have dreaded owning up, but you will be surprised how forgiving people are when you apologise with sincerity. Why make it harder for yourself than what it needs to be?
If you go to the film school, don't demand anything. Demanding will only get their backs up. Explain your case, show your enthusiasm and ask them to reconsider your enrolment application. If they say no, find another school.
Good luck.