I made all the dragons stronger, but i also wanna make paarhurnax uber, However when i tried to edit his stats, the page is in grey color, preventing me from editing it. Does anyone know how to make it editable? and would it break his quest is i edit his stats? thanks in advance.

You shouldn't kill Paarthunax and then his stats do not matter

Open up Paarthurnax in the editor. Look in the bottom right-hand left-hand corner of the tab and you will see a dropdown box with an entry ("EncDragon01Fire" if I remember correctly), and a lot of ticked boxes beneath. Untick all of them and remove the entry. You will now be able to edit Paarthurnax.

EDIT NOTE: I meant bottom left-hand corner. Corrected. Sorry about that.