Ok, I give up! I've done this route twice in each direction, most recently Thanksgiving weekend last November, in a severely degraded S-60, so I figured it would be easy in an X-75. I just don't know how much less efficient an X is compared to an old RWD S. What most people don't realize is that one gets a significant efficiency "bonus" when driving at high altitude, due to reduced aerodynamic drag -- I've been living and driving at high altitude most of my life.
Nevertheless, Tesla drivers have different thresholds for range anxiety. Case in point: another driver just did Tioga Pass in California in an S-85 and charged to 99% despite Nav telling him he would arrive with 40%. He made it with 39% despite missing a turn and having to double back:
Tioga Pass - Model S 85 -- Is it doable??
That route is so easy I could have done it in my 15% degraded S-60 without a second thought.
So, different people have different comfort levels and I can't speak to that of the OP here. Barring unfavorable weather, I would suggest trusting Nav's range estimate and going with that. Or choosing "Plan B" and going the long way via I-40.