heat pump condenser fan not running in winter
-5 (I assume °F) is a too low temperature for heat pump to work properly (usually those stops working at -15°C [+5°F]), so outer unit is simply 'locked due to excessive cold'. Auxiliary heat, in some units, is controlled directly by the HVAC controller and not by room T-STAT.
Anyway, check if auxiliary heat is connected BOTH on HVAC unit and Tstat, if it's connected only at unit side, connect it to the t-stat, if it's not connected, probably auxiliary heat is not present on your machine (if it was ECU controlled you won't have that cold in your house).
For now, you can just buy a couple of kerosene heaters and use those in case of emergency, look for 'zibro kamin' (I suggest a model that can work in case of power failure).