I've tried every combination of normal, bright, inputs 1 and 2, plus jumping the channels together and interactive volume settings.
I assume this means you made sure you used the bright channel, high input, and had the unused channel volume set to 0. Keep using two 12AX7's.
I'm not sure anything is wrong with your amp either. I don't own a 5E3, but the one that I played had less overdrive available than I expected.
Have you checked these resistances?
There are definitely ways to hijack the preamp circuit so that it overdrives earlier. If you want to go down that road, we can start throwing out ideas. But for now I will just assume you are looking for a true 5E3.