Dear Sir,
Go and drop your proposal and leave the rest in the hands of fate/providence/God. Sometimes in life, we have to do things backwards. You might be afraid her dad will reject you because you're not "ready". But there's an equally good chance he could say no even after you think you're "ready".
There's a saying: "you miss 100% of the shots you never take."
Also, "everything you've ever wanted is on the other side of fear."
So, let go of the lingering doubts and set forth to deliver your proposal.
If she's meant to be yours, no power on earth can snatch her away. If she's not meant to be yours, no power on earth can make her yours.
But, for all the love you claim to have for her, do something. Don't leave her suffering in the doldrums where she clings on to hope whilst caressing shadows of you in the dark.
She, too has hopes and aspirations but needs you to be a man now and propose. So that, if for whatever reason, things don't go any further, she (and you) will be free from the shackles of obligation and be able to move on with your lives instead of living in the past with the notions of what might have been!
So long,