If you really want to do battle with freezing weather... stick on pad for the tank and aluminum foil + heat trace for the plumbing. or get an oil filled electric heater, and leave it set at 55-60F.
you'll need to identify your plumbing weaknesses. my KZ for example has the majority of the plumbing inside the heated insulated area, except for the main line from the pump, and the cold water feed to the hot water heater. The main line I wrapped with aluminum and then heat trace. The water heater line I can't get at, it's behind the black tank which I'm not dropping. It's good well below 0F, but does become "slow" around -15F. Those temperatures aren't likely in PDX.