Astronauts on the ISS have proven that living in space even for a few months is extremely unhealthy. Seems like that might be a harder problem to solve than building the space cities.

How much of that is just because it’s not spinning/ no gravity? That plus better shielding should help right?

High energy cosmic rays are tough to shield against. On Earth there’s 60 miles of atmosphere, in space you would have to reproduce that with several meters of dense material.

What if you were orbiting a planet always on the opposite side of where the Sun is?

Cosmic rays aren't caused by the sun. If anything the heliosphere shields us from some of them.

The view would suck.

You'd have to pack nuclear reactors to provide power (though that's a given for any kind of serious activity in space anyway), and your scientific and operational capabilities would be limited/made difficult by the lack of sunlight.

what about food? wouldnt that be the limiting factor?

If you can lift exatons of steel into space, you can probably already afford to solve the problem of direct synthesis of all, and every fertilizer, and probably nearly every other chemistry process just by throwing more energy at it.

Raw materials will be cheap in space, once we crack orbital manufacturing.

Plants convert light to food, you don't even need anything from science fiction.

You still need carbon; plants just extract it from the air using light.

Reuse CO2 and human waste. You need some income, as reuse can't be perfect, but I think it's manageable.