Your big 29GB NAND backup should be named rawnand.bin. Have HJSplit split in files of exactly 2,147,483,648 bytes (last one will be smaller, of course). This is the size Hekate uses for FAT32 SD cards. The files should be named rawnand.bin.00, rawnand.bin.01, rawnand.bin.02, etc. You should also have two small files, named BOOT0 and BOOT1. Put everything in the restore folder, and Hekate should allow you to restore your backup.
How to tell HJSplit that size? I'm only allowed to give em the size like 214748 and no more digits >.>