Finally, have the 3-way switch spiked down.
Along the way, I did find an older non-DCC compatible switch on ebay so I bought it. Found out it was worse. Where the new DCC-compatible one causes a short along 1/2 inch of independent rail (wired underneath to the right-hand rail) between the smaller left-side frogs, the older one has a short on the same spot but the problem rail is much longer, ,part of one of the frogs. The problem/confusion is when using the left hand route, the frog polarity there is controlled by the position of the other throwbar. Does not sound logical but it is true.
So I spiked down the new DCC-compatible after first accessing the wire that ties that 1/2 inch of annoying rail to one of the main rails. I cut the far end of the welded strap thinking to drop it down a hole so I could possibly control it later but once moved the strap broke loose from the underside of that rail. With that short rail now isolated, I tested the switch with my heisler. No shorts now but it did find the dead frogs. I also tested the switch with an 0-8-0 which ran through it just fine. So no surprise that the frogs must be powered.
I thought about using electrical Caboose throws but as listed in paragraph one, it would be confusing. When switching the first throwbar to the left, the 2nd throwbar must be in the proper position otherwise one of the left-hand frogs will short. I went to a logic chart listing the required polarity of the frogs in the 3 routes. I have decided to make a little switch panel with two toggles (2 frogs are always the same polarity) and a chart listing their positions for each of the 3 directions. Now I can use simple caboose throws to control the rails.