What can i do? please help.?

well lets start from the beginning, i have a step mom that has completely ruined my life seriously, she has ruined me and my dad relationship that we used to have, i refuse to like her in any way possible, i hate her with all my life and plan on dancing on her grave when she dies, today is my birthday im 16 finally and what do i get for my birthday i get to watch her child and make her happy and be nice to her, great its my damn birthday and i got to watch her. my step mom has 4 kids with my dad three boys and one girl i do NOT consider them as any relation to me what so ever, she never watches them i mean never, me and my younger brother who is 15 we watch them 24/7 no lie, no one understands they say they do but they really don't, and there's pretty much nothing i can do except leave but i would have to go to court and all that crap, and if i did that then i would break me and my dads relationship forever, idk what to do my family says that i need to talk to someone like a therapist, but i don't have money for that crap and my parents wont do crap for me, because if it doesn't involve my step mom she's not going to do it. but anyways is there someone that i can talk to like online somewhere maybe or just maybe might have someone on here that understand my story? i mean there is ALOT more to it, this is just very little of it, so yeah please help i really need someone that want judge me on this. i have one friend that understands but she cant help we have talked about me running away and all kinds of stuff but we cant think of anything else. and i fill like every time i talk to her about it, im just complaining and talking about myself and i hate when i fill like that. so please please help.