I can't imagine freezing your fresh tank with 60 deg heat inside. You say you've got light bulbs near the water pump and in the wet bay for heat, which along with your other precautions should do the job just fine. I home base in the Oregon cascades and have had my rigs in many super cold winters, several feet of snow for weeks at a time, and temps in the teens, sometimes single digits. I never worry about the fresh water tank, as heat migrating from the living space will keep the large tank from freezing. Like you, I keep heat in my rig, and run light cords into a couple of "at risk" compartments. If things get too severe, I drain it down completely (not a big deal) and turn off the w/h. I still keep the heat on to combat moisture.
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'07 Itasca 35L/W22 FULL-TIMING
1000 Trails - VFW - 5 Yrs Army
"NOT ALL WHO WANDER ARE LOST"