Did the Video out on the Dock work or were you forced to use the Dock with the top popped? All you've described fits a borked DeclROM in the Dock. Did the FDD or internal HDD work? External SCSI?

FPU and NuBus work fine without DeclROM support because they're transparent to the Dock/ROM, being interfaced directly to the Duo's I/O bus across the PDS/Docking Connector. Other Dock services are lost, such as the Video Output, EtherNet etc. on a DuoDock or Dock+ for instance.

A DuoDock or MiniDock amounts to one big, multifunction PDS Expansion Card for a Duo.