One step at a time. I think it's premature to blame the JB3 at this point (though I admit I haven't followed every post in these threads, so maybe the JB3 is the issue, after all.). I'd first confirm the self-modded UA5 is functioning properly, and then worry about getting the JB3 fired up. So, next steps:
[1] test the coax output to any device to see if it works
[2] test the optical output to any non-JB3 device to see if it works
Once we've confirmed [1] and [2] are operational, then we'll tackle the JB3.