The only "no discharge" water in FL are...
The FL Keys including the National Marine Sanctuary and Destin Harbor. In fact, those are the only "no discharge" waters in the entire Gulf! Your ElectroScan is legal everywhere else in FL coastal waters. That unfortunately does not mean that there aren't some marinas that are "no discharge"..marinas are private property and therefore can make up their own rules. So I wouldn't recommend eliminating the holding tank altogether, it just doesn't need to be anywhere near as big as it would if you had to rely on it entirely.
As for any dye tablets...smart thing to do is let 'em inspect and drop one in. They SHOULD know enough to ask if you have a treatment device in waters where it's legal to use one. I haven't heard of anyone running into any FL water cops with "crossing guard syndrome."