The HX is only used for DHW and cannot be moved, as I understand the design of these tanks the HX am using for DHW are moulded around the bottom 1/3 of the inner wall of the tank.
On pipe insulation, the tank and boiler are located in an insulated room I built at one end of the carport. Once they leave there all water lines run through a 4" non vented flexible pipe under a wood deck and thru the crawl space to the root cellar.
I have the water level 8-10" above the draw for the heating loop, temp at the top of the water is normally between 160-170' and I haven't been able to find anything without spending an arm and a leg to check the temp lower in the tank. That being said with a hot tank I get 140' DHW and the electric water heater is set at 130'.
You can get a digital remote barbecue temp sensor fairly cheap. I guess flipping the tank upside down is out of the question? Is that non flex pipe insulated?