The CMake warnings in the initial configure can certainly be safely ignored as they’re just a CMake policy change. As far as I can see your patches to get Geant4 building are fine.
For the build of the application, I would simply go ahead and remove the /home/jmcfee/geant4/geant4-v10.7.2-install/lib64/Geant4-10.7.2/Geant4PackageCache.cmake from the install. It’s safe to do so directly as it will only be used by Geant4Config.cmake if it is present. The only caveat here is if you built Geant4 against any external libraries (e.g. Qt) that are not in system locations, or not pointed to by CMAKE_PREFIX_PATH. If that’s the case, just make sure CMAKE_PREFIX_PATH points to them.