Ok - here's how I fixed my problem with a little more trial and error.
I had several issues attempting to install WAD files (various errors).
Appparently, I was trying to use WAD Manager 1.5 to install CIOS_Fix (which is necessary for just about anything else).
I used Custom IOS Installer to install cios_fix.wad (Finally installed)
This allowed me to install and run "Firmware Downgrader" where I downgraded my firmware to v3.3U - fortunately, I was still connected to the internet.
YEA! Access to my System Menu again!
Now that I know I can recover, I then allowed a newer NTSC game to update me to 3.4U. Time to backup my NAND!
I hope this helps somebody -- this took me at least 2 days to solve.