Well, now I'm stuck again.
I update GEN-D to GEN-D3, open up VSH menu to Flash 0, edit the version text file to 5.50, no problems so far.
I then manually update to the official 6.35 firmware through the GAME>UPDATE folder.
Once it installs, I'm back to the earlier problem where the system won't turn on: the light will go green for a second and then turn off. I can still open the recovery menu and re-install GEN-D, but until I figure out how to get 6.35 installed, I won't be able to install the 6.35 PRO.
Right now the only thing I can think of trying is editing the version text file to 6.35 and see if I can update to PRO from there, but I still appreciate all the help you can give me.