What could Richard III have done in 1483 that wouldn’t lead to either his death and disgrace or the end of the Plantagenet dynasty?
The way I see things, you’re cooked either way. If you do nothing, the Woodvilles rush Prince Edward to London and get him crowned, and from there they control the body of the King and can put whatever decree they want in front of him and can get it signed. You know they don’t like you, and they know you don’t like them, so they can use any perceived slight by you against them to declare you a traitor and strip you of your lands.
If you try and control Prince Edward yourself, by doing what Richard did historically by intercepting him at Stony Stratford and arresting the boy’s uncles, he’ll always remember that, and it’s only a few years till he reaches his majority. He lived with his maternal uncles and kind and barely even knows you. Same as before, you lose your head.
That leaves the third option of taking the crown yourself, and I really don’t see a better option than that