1) That's an optional configuration with extra components to achieve an additional effect, that being lowering the smoke output when you're stopped. The relay is the Axicom IM06DG. The bridge rectifiers are 1.2A rectifiers.
2) The Super-Chuffer handles a single LED for the headlight. I'd run the second ashpan glow direct from the TMCC headlight output, just add a resistor.
3) The resistors in the MTH smoke unit are replaced using a single 20 ohm wirewound 2W or 3W resistor. I put the single resistor in the holes closest to the stack.
I've actually done a separate board since then to give me a more universal capability for smoke intensity control. This is how I do it nowadays. I actually used up the blank PCB's I had or I'd show you a real picture, I have to order more. 
