Try to remember that your sister is trying to help and support you based on absolutely NO knowledge of what is really involved in the issues of child abuse. She is bound to get things wrong sometimes, and yes, when she does it will sound, like, hmmmm...I totally can't match your phrase so all I can do is repeat it!:
a dumbass bitch thing to say! ;(
On you liking guys, fine. If you are gay, then that is part of who you are and there is nothing wrong with that. A loud voice in society sees it differently of course, but "loud" doesn't mean "right".
At the same time, try to bear in mind that for any teenager sexuality is a huge issue and can be very confusing, and for an abused boy it's even more confusing. The important thing here is to be true to yourself, and certainly no one here will expect you to do or act or speak any differently.
By the way...gutsy post.
You're doing great! Just keep it real and you WILL win this one.