Also with vertical farming, you have to think in terms of vertical and time dimensions. You have no more seasons and you get to harvest throughout the year. And you can stack vertically. So, it can be pretty efficient in terms of land usage depending on how high you stack.
As for energy and light needs. Yes, it would need lots of energy but nowhere near what you think. Your back of the envelope math is talking about acres which isn't that useful of a metric for your energy needs. This is the fallacy in your argument. It's not about the light emitted but about the light delivered to the plant. Which depends mainly on the distance to the plant of the light source.
You can actually grow herbs with a kitchen light LED. I've done so. They sure aren't anywhere near as bright as the sun or particularly efficient. But it works. You just have to put them pretty close to the plant to minimize the light losses. That's the whole point of a vertical farm: minimize the losses by maximizing the light usage. Lots of low energy LEDs centimeters away from the plant are much more efficient than big light sources a meter or so away. And what happens to the light that "misses" the plant? Very simple it either gets absorbed by something and turned into heat or reflected by something back to the plant. And of course you'll find lots of reflective surfaces in vertical farms for that reason. Ultimately a lot of it gets transformed into heat. Some of that is useful. Plants grow faster at higher temperatures. And some of that is a cooling problem. Which takes more energy.
Vertical farming feasibility is mainly going to be a function of price and availability of energy. And as energy is the most costly component, yields measured in tonnes per mwh are a more sensible way to think about the feasibility than tonnes per acre. Acres are not that useful as a metric for measuring energy usage. They are useful for traditional farms mainly because land is expensive and you can't stack your crops on it. But it's a useless notion for measuring vertical farm production. How do you even measure acres in a 3 dimensional environment?
So the real feasibility just depends on cost per mwh. As that comes down, a lot of things become feasible. Including vertical farming all sorts of things. It's a cost curve. Right now energy is to costly and yields are to low. There's a point where those curves cross and things become feasible.