It is always OK to ask questions, that is how we learn. Our knowledge base is always subject to upgrading; that is the fun part!

I am presuming you are speaking of an old steam locomotive with a 4 wheel trailing truck.
1) There are a number of things that can cause the wheels to derail on a switch.
First, using a caliper, check the spacing of the wheels (the 'gauge'), taking your readings where the flange meets the wheel tread on each wheel, and compare it to the rear wheels of the truck. Then compare the reading to that of the front truck wheels. The wheels may be a bit too close together, or too far apart. The readings between wheel sets should be very close, certainly no more than .062" (1/16th inch) difference.

If the rear truck has a conical spring that presses a rivet head to the underside of the rear drawbar, check to see if the spring has lost tension. The spring tension is needed to help keep the wheels on the rails.

Another cause could be a slightly bent axle.

The number on the locomotive, and approximate vintage would help in narrowing down the problem. A clear picture of the truck underside would help also, if possible.

2) You should consider using a second transformer exclusively for your accessories, so as to have all the available power of the CW-80 for your trains.
Better yet, consider upgrading your CW-80 to a more powerful transformer so that you have sufficient wattage to power your trains, and enough reserve to expand. You can then use your current transformer for the accessories, with plenty of power to spare. You can check your local hobby shop or online stores and auctions for good, used high wattage transformers such as the venerable KW and ZW transformers. With the KW you can run 2 trains on 2 separate loops, and the ZW will allow you to operate up to 4 trains on 4 different loops. You can never have too much power, and the older transformers give you more wattage for the dollar than the newer transformers do, especially if you do not need all the bells and whistles the newer transformers have.

*One way to keep your wife from telling you to put your trains away is to involve her in the hobby! Buy her a train, or let her help choose accessories or help with scenery. Many men have won over their wife this way.

Larry