So... here we go...

Make the planet fit the original shot with blurred edges is a fantastic idea. Also, i'll try to color correct the planet if it is the case.
Make the planet smaller.... its impossible... because i had to make the planet fit with the death star borders, to "erase" the death star. And also, the scale factor has to be in the timeline, because of the zoom in the original shot.......i dont know if you are understanding this.... but anyway, sorry but is impossible.

Ps: Well not quite impossible, but it would take a long time.

PsPs: Like a really a long time, i would have to remake all my work.