iPhone could not be restored. An unknown error occured (28)

well, ralph could be right.

but eric, i miss something in your description - there is nothing about cleaning and nothing about flashing the phone with something like irecovery.

did you disassemble and clean the phone at all???

if not - get the tools and disassemble it, clean the logic board and the connectors with ipa and a soft paintbrush, look out for odd looking stuff (white/greenish and black burnt parts)

take also care about the dock connector. a shorted nand flash could also produce errors - but that would be a little bit tougher to fix and i think you should start with the stuff i mentioned above

good luck