Thank you for your update.
When using the B-U terminals to run your trains, you can vary the voltage throughout the range of 10-18 volts by moving the voltage select arm on top of the transformer. You should be able to slow down and speed up your trains satisfactorily with your transformer. The only downside is the transformer varies in 2 volt steps, but that was the technology of the era.

Should you wish to replace your transformer with another one, either a used KW at 175 watts, or a larger ZW transformer at 250 watts are good, and virtually indestructible. The KW will allow you to run 2 trains simultaneously, and the ZW up to 4 trains simultaneously, on different tracks of course.

When you expand your layout, you can add more lockons to the track to better distribute power.

Larry