Robin, only you know what's right for you. But you asked my opinion.
As far as living with your inlaws, you might be wise to work first on being independent (as long as you think that's doable). It would make transitioning easier.
As far as being obese, I would suggest NOT WAITING to be thin. Too many people waste their lives away with what they'll do when they become thin, and never get there. IMO, there's no reason a heavy person can't transition.