Questions: Family & Friends

I just turned 15 and he's been married to my mom since I was 4 so I basically see him as my dad. I've never felt awkward or uncomfortable around him until recently.
My body is shaped similar to this



One day he mad a comment like, "you look like your dad but you're shaped like your mom." I just said "oh" awkwardly and did an awkward laugh and he continued with "you inherited her backside that's for sure." I had to leave the kitchen after that. After that day the weird comments just kept going on and on. He comes up to me and asks "you've had any grown men hit on you, yet?" I was just like "what" and did the awkward laugh that I always do when I'm uncomfortable. He just says "you're pretty and you have a beautiful shape you don't exactly look your age." I don't know, maybe its just me or maybe he's just naturally awkward and creepy af. But, it hasn't happened before so that's why I'm so ewww about it.

Every since they started dating which was about two years ago he always made me feel uncomfortable , he tried walking in on me coming out of the shower, another time while i was in my room sleeping i heard him open my door and he was just watching me sleep - i heard him because he’s a loud breather. Everytime i shower and he’s here he is usually in my sisters room and there’s just a crack open and i could see him through the crack, like he can’t close the damn door? One time when we went camping there wasn’t much space to sleep so it was him my sister in the middle and me sleeping on the other side and in the morning i knew he was already somewhat awake and his hand skimmed touching my ass. What I’m trying to get here is that my sisters boyfriend makes me feel uncomfortable and i want to tell my sister but she has psychological problems and she’s emotionally dependent on him, therefore i feel if she gets all this information she will cut herself or something. What should i do should i tell her or just wait? I’ve been waiting for them to break up but she’s just too comfortable. I’m not completely close but i just think she’s wasting her time. And PLEASE NO PERVERTS THIS IS A SERIOUS MATTER. I’m honestly really scarred and uncomfortable. I told my mom already and she did nothing..