There's a Firefox addon called Lazarus that automagically saves and restores everything you type into web forms. It's designed for recovery from crashes, so I don't know if it would help with the particular loss you sufffered there. I've found it invaluable.
With that, Firefox in Login Items, and the box ticked in System Preferences for automatic restart after power loss, it's as if the Mac never went down in the first place
Back on topic: If the OP requires use of the PDS slot for the Apple II card, that's going to restrict the choice of motherboards quite a lot, especially if networking is also required. If onboard or slot Ethernet proves unavailable, consider a Localtalk to Ethernet converter such as the Farallon Etherprint, or another Mac running Localtalk Bridge. Or a SCSI->Ethernet converter.
I agree that a CC with 575 would be the most elegant, but it all depends on the resolution of the issue described in the Apple technote linked above, and of course the availability of a CC. If a 575 proves unviabe, perhaps a 520 or 550.
5) What logic board upgrades are available for the Color Classic?
Not if you want the PDS slot for a ][e card.