Right you are, when you're the only game in town you can charge a premium. That said, it is an option and people have a choice not to pay for it (as I did on the AP2 car - $5K not worth for TACC and auto-steer is far from safely useful as it requires constant attention to make sure you catch the whatever the low percentage of the time it's going to screw up - even Tesla says so with their warnings/disclaimers).
Absolutely, this is by the way Tesla's biggest advantage today as cars like Bolt have already caught up and actually passed the Model 3 since the former is already available while the latter is still "coming soon". It's a little bit of a chicken and egg situation, no chargers means less EV sales, less EV sales means no need for chargers, But let's say GM was to throw some resources at it, how much do you think it would cost to match Tesla SC network? There are 366 superchargers in the US, if GM was to put $400M at it they could probably get there in a year, no? World-wide there are 871 supercharger, so less than a billion dollar barrier to entry. Problem for the likes of Fisker or FF, but not GM if they really wanted to get there.