Hope you don't mind if I refer to you as Star. I believe it sums you up far more accurately. Anyhow...
From what you write, you're definitely on the rise:
- You've risen to try and meet the challenges that came with moving to live with your Nana, away from your parents. You're a star, simply because you've put effort into adapting. I can't imagine how difficult that must have been for you and still is
- You've risen to the challenge of seeking out schooling opportunities (debating etc). You're a star!
- You've risen to the challenge of accepting a job. You're a star!
- You're rising to the challenge of considering a future in nursing. Yep, you're not only a star but a caring one!
I'm sure the list goes on beyond what you've spoken of. By the way, I know the debating and job didn't pan out based on what you said but that doesn't stop you from being an absolute legend in all areas, given your interest in the first place.
Is it possible when you next visit your dad to talk with him about all your goals and ask him how it is he can actively help you achieve them? This might give you a firm sense of direction, especially if he's enthusiastic when it comes to helping raise his beautiful young star (you).
The loyalty and love factors...hmmm. Whilst your nan has raised you in certain ways, it sounds like she also see-saws by putting or bringing you down. This must be incredibly challenging, all the ups and downs of living where you are. If you're seeking consistency, perhaps your dad can offer it to you. You can still love your nan and visit her.
The role of your primary guardian, no matter who it is, should be to raise you (to meet your full potential), not have you sink down into a depression of self doubt. Guardians will often carry their own psychological baggage for whatever reasons, which leads them to behave the way they do, but it shouldn't be baggage that weighs you down and drains you.
If you do decide to live with your dad, this is a challenge your nan and mum will have to come to terms with. Such a challenge is not your responsibility. If people are sabotaging your efforts to rise, the most responsible thing they can do is either change their ways or let you move on to be raised.
I'm mum to a 14yo boy and 17yo girl and they know that in raising them one of my goals is to drop my baggage bit by bit as we bring each other up. They're great teachers and guides in my life and they deserve to be raised with full consideration, just like you do.