Your heatpump seems to work fine, it the generates the correct amount of heat within specs, but your KWHs do not indicate high run times. This in combination with your not reached setpoint suggests that your distribution system (ductwork, blower, dampers, zone controller etc?) is not able to deliver the heat to the house. The pump capacity seems to be fine.

Thank you, all, for your time and expertise. I think I am making progress -- at least I'm beginning to feel comfortable about knowing where the problem lies.