Have you tried a basic setup already. With basic, I mean without the switch2uneek program.
It's best to start with a sneek setup. It can run without a hdd, so if that disk is incompatible, it doesn't matter.
If that one is working, you know that your emulated nand is working as expected.
Next, you could try a uneek setup. All you need to do is copy the emulated nand folders from your sd to your harddisk.
You also need to change the kernel.bin in the sd:\sneek folder, and you also need a sneek folder with the same kernel.bin on your harddisk.
When that's working, you can start with uneek + di. Make sure you have at least 1 game in the games folder of your usb drive.
Add the di.bin and font.bin to your sneek folder of the usb harddisk.
You might also take a look at my tutorial. It describes the startup sequence with a modmii created nand in detail.
Note that the sneek + di created with the files of my package is not the same as the general sneek. Mine are looking for the nandpath.bin file and search for the nand folders in the location speecified in that file. My di from that package emulates it's dvd from sd instead of usb.
If all these things work, you can add the switch2uneek as a last step.