Re: fat32 support
Yes, nuni supports FAT32. Its MBR code simply runs whatever code is there to be found at the beginning of the partition.
Out of curiosity, without even using the instructions to install nuni for Linux, I tried just copying the nunimbr.bin file to a floppy's MBR.
Then I popped that otherwise blank floppy into a machine that has Windows 95 installed on a FAT32 partition. The floppy's MBR code asked me which partition to boot, I told it where Windows was, and Windows ran as usual.
It didn't work when I told it where to find Linux on the same hard drive, but I suspect it would've worked fine, had I installed grub in that partition's boot sector, not in the whole hard drive's MBR, where the floppy's MBR code wouldn't be looking for it.
So, if your access to a hard drive is already at least good enough to let you install Windows on it in the first place, and if no program on your Windows system scans the MBR and mistakes nuni's code for a virus, I think nuni can be expected to get along very nicely with your FAT32 partition.