I did not read this entire post, but I'll ad a few cents worth if it helps. I use a Taylor wood heater. A buddy does the same. His was running the pump 24/7 and was eating a bunch of wood. His heat exchanger in his gas pack went out so he added the woodheater with the heating coil in the duct work. First he ran the pump 24/7, then wired it to run only when the heat was needed. His problem then was getting 4-5 minutes of cold air until the hot water got back to the coil. I added a timing relay. It called for heat, the pump came on, after the time delay it let the blower fan come on. We timed how long it took to get hot water back to the coil then added 5 seconds to the time delay. Wala, hot air when the fan came on. He cut his wood usage by 1/3. His heater is 300ft away running 3/4 Pex with cheap stick foam insulation slid inside a drain pipe with "Great Stuff" spray insulation buried in the ground 1ft.