Great job so far. I have a suggestion for heat.
You are currently using precious electrons to generate it. Meanwhile, you have a fairly hot motor under the hood. Why not get a length of fairly small diameter flexible copper tubing and wrap that motor, good and tight. Cover it over with fiberglass batt insulation. Install a small 12v circulator pump and run the coil directly to the heater core. I would leave the resistance heating in place for when it is needed (sitting in traffic or at start up).
During thw warm weather either remove it or add another heater core somewhere under the car to bleed off the heat.
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