You will not be able to upload/download configuration files to that remote without ProntoProEdit Next Generation (PPENG). I think some have been successful here with Parallels on the Mac.

Tonto only works with the first Gen Pronto TSU1000/2000/6000 and EU derivates of those remotes. The Marantz Equivalents use TouchScreenSetup (RC5000/5000i/5200/9200).

You can put a 3500 config on the 7500 but it will be migrated because the Black And White 3500 uses a palette-based transparency scheme whereas the 7500 uses Portable Network Graphics (PNG) files that have a transparency layer. As such, any 3500 config you load, you will likely have to change images, expecially if your buttons have rounded corners, etc...