@FallonAngel I think I know a couple of things that were biting you that catch a lot of new owners off guard.
I felt that I would be good, I mean the 3 has a range of "320 miles," right?! Well not so much as I found out,
at around 80mph between Indy and TH
Oh, for Pete's sake! This reminds me of a coworker who was just telling me about his recent trip that was 280 miles, and he said, "So I charged up to the full 310 miles and got on the highway and set my cruise control at 85." So people think they can match EPA rated range whether they are going 35 mph or 85 mph?
But you say you were going slower on the section to/from Terre Haute and Princeton?
and then 65mph between TH and Princeton
But...
had some alert popup stating that I needed to drive 65mph or slower to reach my destination,
Ah, so actually you were driving faster than that, and then it finally had to warn you to slow down to 65 mph.
So now we've gotten more to the truth about your speed. Being able to match the EPA rated miles usually needs to be about in the 65-70 speed range. If you are going above that, you're going to be running through "rated miles" faster than 1:1 with your real miles. And that's not even accounting for any heat, which will reduce that a bit more. It's the same pool of energy that has to supply miles + heat.
So on to the things with climate control. These things are more the car's fault that can be fixed, but you didn't know about them yet.
Another big gripe for me is the damn windows kept fogging up and I was making a point not to run any heat to get as much range as possible. But I was forced to run defrost so that I could see out of the front window. I did that for 5 minutes at a time, maybe 5-6 times on the way back to the TH SC.
The choices the car makes for the fully AUTO mode are generally kind of wrong all year round. In this kind of cold/wet situation, here's the specific problem. AUTO thinks that it should be using recirculate and air conditioning + heating.
That is pretty stupid and results in a few problems. Recirculate of course traps the inside breath-filled air, so it fogs up the windows, as you discovered. The car thinks it will compensate to dry out the air by running it through the air conditioning system. Well....but that does also chill the air, which means it then also has to apply even more heat to it to keep the temperature. So with the heating and the air conditioning both drawing more energy to fight each other, it shows up as really high consumption along the trip. I've seen a few threads of people discovering this. The wetter it is, the more this effect shows up. Your thing of turning on the defroster will temporarily remove it, but won't keep it from continually happening.
The very simple and obvious fix for this is to turn the A/C off to make sure it doesn't run and switch it to draw outside air through instead of recirculate, so it will keep sending new air through the car instead of letting that moist air build up inside the cabin. That will reduce the energy use and the window fogging. Also, you might need to keep the fan on at least 4ish to keep the air moving, because if it is at the set temp and puts the fan down on 1, it's not enough air flow to keep the fog off the windows, and it's about like recirculate.
I mentioned about AUTO being wrong year round. The summer effect is that it always wants to use outside air with the air conditioning. I don't know why it is, but I find that for the same given fan speed, it blows half as hard from outside air than from recirculate, so cooling is way less effective. Maybe this is a Model S/X effect that the Model 3 doesn't suffer from with the different venting system it has.