Overall, this should not be this difficult.
1) First make sure that all of your .wav files on the Mac are 16 bit, 44.1.
2) Format your zip disk on your MPC (FAT 16, MS-DOS by default) OR format your zip disk on your MAC (FAT 16, MS-DOS, bootup option is not needed.)
3) Put the zip disk in your MAC and copy the files - NOTE that filenames will be truncated if the filenames are over 8 characters (FAT 16 standard.)
4) Put the disk in the MPC and load each .wav - this will take lots of time since you have to load each .wav in separately. MAKE sure that you are not using a folder for the 2K classic - it just won't work.
5) I would use MPC program-maker to make a .PGM file for loading in the MPC.
6) Lastly, the MPC classic is a delicate box. You must realize that when you start eating up large amount of RAM that YOU WILL inevitably run into problems because the MPC NEEDS its own RAM to shuffle, move and handle data around.
7) I don't know why you'd want to load up such a large kit, but if you want to, I recommend loading up smaller amounts of .wav's. You can then just append to what's in your MPC memory.
Work smarter - not harder.
Peace