Brandon,
Welcome. You've come to the right place.
Many, many people on this forum swear by the older stuff, and rightly so. However it needs loving care in order to perform.
Have you had the chance to clean and lubricate your two steam locomotives?
Also, your photo doesn't show us the specific transformer (controller) that you've use to get the K-Line MP15 working. It would be helpful for us to know the details.
You may be caught up in an AC vs. DC thing.
Nice progress so far. Don't give up.
Mike