Thanks for the kind words. It's getting to the exciting part!
It occurs to me now that I should probably contact Paul Pratt to share what I've learned, or find some other way of preserving and sharing it. Unfortunately I can't publish my commented ROM disassembly for the same reason you can't publish the ROM contents. But I've put a lot of work into reverse-engineering a documenting the purpose of many of the routines in ROM, and it might eventually be of interest or use to someone else, so maybe there's a way I can share it.
The Altera DE1 board that I'm using is $150. It's a great place to start, but isn't perfect for this project. It has only 512K of SRAM, and no way to hook up a mouse and keyboard at the same time. It also has some other components I don't need that just raise the cost. Eventually I hope to create a custom Plus Too board with Mac-specific parts. If there's enough interest, I guess I could sell additional boards or kits, kind of like dougg3's doing with the IIci ROM design. I'm not sure how much they might cost... maybe about the same as the DE1 board.
I used a tool that's part of Mini vMac to disassmble the ROM, which provides a dump of all the CPU instructions in the ROM routines. The tool also adds trap names, some constant names, routine names, and a few comments, all of which I believe were derived by Paul Pratt from his analysis. So for example, most references to the VIA appear using the constant "VIA" instead of the literal address $EFE1FE, and several key routines have meaningful names like P_mBootBeep. That's been a tremendous help, but it still left many huge blocks of hundreds or thousands of instructions whose purpose was totally unknown to me. Most of what I've been doing during the past few weeks is digging slowly through those, trying to reverse engineer the pieces that look relevant to the boot process. As their purpose becomes clearer, I've been adding lots more comments and assigning names to previously unnamed entry points, like P_ShowHappyMac.
It occurs to me now that I should probably contact Paul Pratt to share what I've learned, or find some other way of preserving and sharing it. Unfortunately I can't publish my commented ROM disassembly for the same reason you can't publish the ROM contents. But I've put a lot of work into reverse-engineering a documenting the purpose of many of the routines in ROM, and it might eventually be of interest or use to someone else, so maybe there's a way I can share it.