Outstanding, I'm happy for you, too.
Regarding wheel resistance,
most of my users model retro, as in they run cabooses (cabeese?). The general practice is to install a loading resistor in the locomotive and in the caboose, not bothering with the intervening cars (wagons).
I used 5K6 to illustrate because it is a common value for wheelsets as sold here. Using only two detectable cars per train, loading isn't an issue. Frequently, I recommend 470 ohms for the loco and caboose both. Combined, that's less than 65mA extra current. (500 ohms @ 16 volts = .032A) Insignificant..... 10 resistors @ 5K6, paralleled, would be 560 ohms. ~30mA... Perhaps better, as flicker from one car won't drop the signal.
My recommended practice is to fabricate a circuit such as you would use to light a passenger car. Metal frame trucks and conductive axles, attached to a plastic underframe. A 6mm strip of .1mm (1/4" x .0035) brass shim stock is drilled to match the bolster, for each end. Long enough to reach past the axles under the frame. Then solder a resistor between. Cheap and quick....
Looking at your signal logic circuit, it looks very familiar...
Were you to analyse my elementary, I think you will find it's about the same, merely two iterations of the circuit to provide signals for both directions. Bi-directional traffic is very common here because of the distances.
Best of luck with it. Now the problem is solved, you can go play trains! Perhaps you might appreciate this:
**broken link removed**
I was in Wellington, N.Z. in the late 60's. This showed up at a convention in Aukland at the 68 meet. It made the rounds in the 70's, I'm trying to get it started back up. The older I get, the better it reads....
One last thought; I have tried simulators, long ago... They worked well for digital circuits. But now we have PICs and the like, my designs are passe'. I never had much luck doing analogue circuits with them. Perhaps two or three generations of improvements have corrected that. Much of my work has been with low level industrial instruments; a strain gage has 0-20mV full scale output. Keeping signals like that clean around welding operations takes some finagling. These days, I have a library of circuits in my head that I simply apply without thinking about them. As a novice, you probably were pulling out your hair over my comments. For that, I do apologize.
Bill Hudson