Great stuff, interesting pics and I also have an interest in 'period' music....
Likewise with loco numbers running into 3 digits I also use 4 digit addresses. The Prodogy has an interchangeable output for prog track or POM, one I have tested the install on the prog track I then program 'on the main' as this is necessary for setting up sound files. I can understand what you mean about express steam but the best chips are now pretty good at higher speeds for realistic sound. It is best to have all the locos at a lowish level so that it all does not get overpowering and it is best practice to shut off stuff that is not running, especially diesels.
I will see if I can dig out a couple of pics of my micro layout, the big one is still just plans at the moment....
Cheers
Tim