You can look in the .LST file to see the addresses where each variable is assigned.

You can also File > Import the .cof file into MPLAB then View > File Registers > Symbolic Tab.
It's a lot easier to read than the .lst file.
Of course, you need the datasheet to figure out where the banks are.

And there are many PBP commands that use the FSR.
But none of the statements in your ISR do, so right now there's no need to save/restore it.

Cheers,