Welcome to the forum, and thanks for your pictures and explanation of your modification!
You may wish to look into these drop-in replacement LED's for your switches and controllers.
http://www.autolumination.com/trainbulbs_leds.htmThey have overvoltage and overcurrent protection built in, so you just screw them in with no external components necessary. Rated at 14 and 18 volts, they will work very nicely on older switches, accessories, locomotives, passenger cars, etc.
Larry