Hmm, that's strange. Most likely it would be the ROM. You might want to try downloading it from a different, more reliable source. Or you could also download SnesTool and fix the header; that might be the problem. But if I were you I'd just get a different ROM. If there's something wrong with the ROM right now you don't want to risk having more bugs with it in the future.
As far as your other questions, can't answer them, don't have a Disk Dual *yet*.
Jigsaw