As to the 50 degree and below E-Ray not allowing Stealth mode

It is only true for Stealth mode, which operates in eFWD for up to 45mph/4 miles.

The reason is the E-Ray shares a carryover Stingray HVAC system, which does not operate when in EV only mode.

Lower than 50deg has risk of flash fog/frozen windshield conditions that are unsafe, and we have no functional way of solving it,
so there is a temperature threshold.

The actual eAWD system is absolutely functional below 50deg and operates well in extreme temperatures as long not in Stealth only mode, as we put it through the paces in Michigan winters for several years and even Colorado!
The E-Ray is so fast, a total riot to drive. Hope you get to drive one soon, it was an awesome project to work on.

This is published in owner's manual, so people are not reading it very well :

E-Ray Stealth and Shuttle Modes Climate Control Operation

Climate controls, including defrost, are not functional while in Stealth and Shuttle modes.
Heated seats and steering wheel and ventilated seats will remain functional.
If heat, A/C, or defrost controls are pressed while in Stealth Mode, the engine will
Automatically start, and the climate controls will be active. See Driver Mode Control page 195.

If the vehicle was started in Stealth mode, Auto Stop will not be available until the next ignition cycle

Stealth Mode :

Use to silently exit your residence before the engine turns on for maximum performance capability.
The typical range in Stealth mode is about three to four miles depending on the starting SOC, vehicle speed, and other driving conditions.
The Stealth Drive Mode Capability Gauge on the instrument cluster informs the driver of when the engine will start, see Stealth Drive Mode Capability Gauge page 85.

Stealth mode automatically deactivates if the following occurs:

. The vehicle speed exceeds 72 km/h (45 mph).
. The outside temperature is lower than 10°C (50°F).
. The high voltage battery SOC is lower than 21%.
. Quickly depressing the accelerator pedal.
. Depressing the accelerator pedal beyond one-third of the way.
. Turning on the climate controls. See Dual Automatic Climate Control System page 149.
If one of the conditions occur, an indicator on the Driver Information Center (DIC) displays explaining Stealth mode was automatically deactivated.
When Stealth mode is deactivated, the vehicle will transition into the default driver mode.