Several of these questions might be answered just by going to your colony and clicking on the good in question. Compare, for example, the production of drugs at Chicomoztoc (probably 5, like in my game) with its consumption (probably 8, like in my game) and you'll see why there's a local shortage.
As to whether they're an exporter, yes, they are. Goods are abstracted to approximate mere orders of magnitude, so - while the numbers probably don't line up *exactly* like this, it'll be correct in broad strokes - producing 100,000 of a thing while demanding 100,000,000 of it would indeed leave you at a shortage, if your incoming shipments either could not meet demand (in my game, there are no 8-magnitude suppliers) or were interdicted one way or another. So while Chicomoztoc applies 100,000 (or whatever the 5 is meant to represent, you understand) to its own needs, it can also apply 100,000 to supply because you can supply several 5-magnitude demands before approximating a 6-magnitude demand.
Is raiding worth doing? Well, if you want to be Space Medellin, then it's good to take out the competition but generally speaking if you can just out-produce them by an order or two then the difference of hitting their supply will be fairly minimal. Raiding is probably more valuable as an asset for inducing instability.
edit: upon re-reading I see I managed to write all that while only answering two of your four questions. Sorry.
Smuggling occurs even if you're not a free port, but you can only directly profit from smuggling if you're a free port.
I don't believe drugs are an exception to the general raiding rules - supply and demand work like other goods, and instability is tied more to the industry than the production itself though there's obviously a direct penalty for running shortages
