Jim, I am amazed with your extensive knowalge of electronics, if only I were so enlightened.
Relieved and cheered when I learned of a buddy that would be returning to my area via Elkhart, IN., I asked that he snoop around the RV outlets for a dimmer/rheostat that would handle 1.5 amps. Eureka! Yesterday he said he had located one and is bringing it home. Thanks again, "Sparky."