Just going to highlight a few things you said.
All-Interstate
no stop and go
Both of these on a traditional gas car mean better range. Stop and go is bad in a gas car. Highway driving is better in a gas car.
In an EV it is the opposite. Highway is worse. Stop and go is good because you regen when you stop (you still come out negative net energy, but the impact is far less than a gas car). At a stop light you use almost no energy in your EV. Pretty much just your HVAC which will be minimal most of the time.
Speed kills range. Interstate speeds (you didn't mention how fast you were going) can really impact range. In your EV your biggest energy draw is drag, and drag increases with the square of speed meaning it goes up exponentially as you go faster. Range at 80 MPH on the interstate will be way less than 55 MPH on a secondary highway.
This is all normal. Unfortunately, when you switch from a gas car you come in with the same expectations you had in your gas car, but now they are reversed. In a gas car highway range is the best, but that's because gas cars are just so horribly inefficient in the city.
My best advice is to use the navigation to plot your journey, and the energy trip graph is generally pretty good at guestimating how much energy you will need, and in your case, it would have thrown a supercharger stop in for sure. The energy graph is surprisingly accurate.
If you ever feel like you won't make it home or to a charger, just decrease your speed and your consumption will go down a lot. But if you use the built-in navigation, it will tell you where and when to charge anyway.