Dude, you're parents are not going to kick you out. If they have known you have smoked for awhile, they aren't now just all the sudden going to really kick you out. They are most likely just threatening to kick you out because it's obvious you disrespected THEIR property with your drug habit. I am sure they don't really like it in the first place that you smoke, but if they have known and not really cared that much...then they obviously aren't totally against it. HOWEVER you using your dads knife to scrape resin probably really pissed him off because it was probably crossing the line. Not a good idea to disrespect your parents property. I think the times I disrespected my mothers property were the angriest fights ever.
I would say, quit toking so much...don't be stoned around your parents...and don't disrespect their property. You are only 15 years old, your parents aren't going to kick you to the street becaues you smoke pot. Plus, being 15 you are still really young and could be put in a childrens shelter still, with all the kids whose parents abandon them...or all the kids who got in trouble.