It sounds like you've got a plan but I don't think you need to go down to 117. When I was 15, I was only 5'3 (still am) which is a lot shorter then you are and I was 115 pounds and a size zero so since you're a lot taller I don't think you need to go as low. (I've gained weight since so that's why I'm here, I'm up 15 pounds of pure fat, looking huge but wanting to be thin again)