I have not read all the posts, forgive me if I am repeating something someone else has offered.
Allow no parking at all on the Street coming from Tropic Air to Tarpon Street. Right turn only at Tarpon Street. Change the flow of traffic on Middle Street to go the opposite direction, traffic going through town can stay on Middle street all the way to the bridge, others can continue on to Front St.
Close off the area of the park from the street that Gecko Graphics is on to just past Fido's, like they do every weekend night, and have passes for Front street employees to park legally all day up to and after those points. The Street Gecko Graphics is on would become a street that flows from Front St. to the Lagoon. Any others have 30 minute parking limits. This still allows boat passengers to hail a taxi. They can go down the side street and turn on to Middle street to go north or carry on to Back street to go south. If Town Board wants to make money, invest in parking meters.
During high volume school hours, close Tarpon Street off at the school gates, allowing traffic to only turn left on Middle Street. Front Street would remain closed so children can safely walk at lunch time for 1.5 hours and after school for 30-60 minutes.
Make Back Street a South only street passing by ElFogon or the other street just past ElFogon.
Make the divider at Tropic Air two way so that traffic continuing south past Ramon's Village drives on the Tropic side of the divider and traffic to the lagoon and San Pedrito is in the Save-On side of the divider. (I have seen traffic going both ways on both sides). Traffic would have to cross if someone is turning back into town, so perhaps an All-Way stop would have to be used. Caveat: I am not an engineer so, like Phil, I await the spotted flaws ;-)