of it is a star with a circle around it, it is a Capitol If it is a dot, it means a town, especially if there is a name next to it.
Depends on what you want to do. If you want to go swimming of course summer(or maybe a little sooner to avoid the crowd). Note that all seasons but summer you'll find that the islands have very low temperature and much wind/rain. I think the best time to visit Greece is September. Weather on the islands is still hot (85 degrees) but not really that many tourists in September. Therefore room prices are about half. Still hot enough to swim. Also, ferries are still frequent between the islands. By October the ferries don't run as frequently and most businesses like restaurants close down. I absolutely wouldn't go in July or August. Too busy. Too expensive.
The driving distance from Fort Worth, Texas to Cancun, Mexico is about 2,127 miles.
About 12 hours. You would need to change planes, probably in Memphis TN, as Nashville isn't a hub for transatlantic flights. (Memphis-London takes about 9 hours 15 minutes). You may find it more convenient and/or cheaper to fly from Memphis.