Order the octopus. The fishermen dry it on lines and poles near the harbour — you'll see it before you eat it, which is the right way to understand where your food comes from. Grilled simply, with lemon. Don't overthink it.
Astypalea is the Greek island you were looking for when you booked the other one. A butterfly-shaped Dodecanese island where almost nobody goes. Go. Stay in the Chora. Eat the octopus.