Lots of blankets then. However if its hot.. Yeah... Not so smart. Well you could just stack stuff in front of your door or find a way to jam it. At my old house I drilled a hole through the trim and the side of the door and made a cap for it(fairly small hole, no atom bomb crater type hole). Then used a nail to make it so the door wouldn't open. Usually wearing at night depends on how nosy your parents are. If they do not normally bug you go for it I wear at night all the time with no problems. A few close calls, but mainly that was my fault.
I agree - it mostly depends on your parents. I don't think mine have entered my room without a good reason or without asking after I was like 12 or something. I fail to see why they would just enter for no reason at all in the middle of the night.
If they wake you up in the morning, you will have to buy an alarm clock and teach them that you can wake up in time without their interference.