You should probably just keep annoying the crap out of him. Call and text him constantly
if you can survive without needing that 725$ you should forget all about it and move on.
Your dad is a very good man. He must have been using it for good reasons. I must think that you should let it go for a while, and let him become more secure in financial concerns, then let him pay you when he is ready.
Regards,
Infurious.