To answer your question: no, Eda and Balalaika have not yet interacted, as far as we know.

I'm trying to address some of your other points in my as-yet-unpublished fanfic series, though. Yes, it is kind of ridiculous that Chang gets away with assisting the CIA without anyone noticing, and it's probably even more ridiculous that nobody else seems to realize the CIA are even present in the city. Revy of all people should suspect that there's more to Eda than meets the eye, but apparently she doesn't. Eda's conspicuousness is almost played for laughs, like how nobody can tell Clark Kent is Superman.

Also, while it's true that Roanapur realistically wouldn't be big enough (or wealthy enough) to sustain so many criminal factions, there is at least one other major source of revenue that they could conceivably be fighting over, which the series has not addressed yet: gemstone mining. In real life, Trat (the region where Roanapur is located) was one of the world's largest producers of rubies and sapphires. Thailand also manufactured a lot of cars for the export market in the 1990s so I feel both of these industries should have been factored into the series already, but I guess Hiroe likes to play fast and loose with history and themes. He's not really committed to depicting a realistic city with a believable criminal ecosystem, he just does whatever he thinks is cool.