You point out the term Adriatic sea is mentioned in Acts 27:27 which is correct and today Malta is not included in that area. However, during the first century the term the Adriatic sea encompassed a much larger area than it does today. That area did include the modern island of Malta.
There are some better clues in the text, Acts 27:7 (NIV) “We made slow headway for many days and had difficulty arriving off Cnidus. When the wind did not allow us to hold our course, we sailed to the lee of Crete, opposite Salmone.” They were forced to turn away from the course that would have carried them to Mljet. This change in course eventually placed them at anchor at Fairhaven Crete, again because they could not sail north.
Another clue comes when they weighed anchor to go from Fairhaven to Phoenix. In Acts 27:14 (NIV), a wind of hurricane force, called the “northeaster,” swept down from the island. (Other versions state the wind came from the ENE). The ship was caught by the storm and could not head into the wind; so we gave way to it and were driven along.
The next course clue is provided in Acts 27:16 As we passed to the lee of a small island called Cauda, we were hardly able to make the lifeboat secure. Cauda is west of Crete.
The next clue comes in the following verse Acts 27:17 (NIV) Fearing that they would run aground on the sandbars of Syrtis. These sandbars are located west of this position.
Using these clues, we have a line that runs from their starting point (Crete) past Cauda directly heading for their biggest fear the sandbars of Syrtis. They had little control and no sails and were being driven in a westerly direction. This course could not north to Mljet.
You are also correct, there are no poisonous snakes on Malta, TODAY. There are many other island countries in the world where snakes have become extinct.
The inhabitants of the island are referred to as barbarians (28.2: barbaroi). If this was Malta, I think they would have been Punic-speakers, so speaking a language similar to Hebrew--would Luke have called that tongue "barbarian"?
Adria originally applied just to the northern part of the Adriatic but the use was later extended. I was told once that there was no evidence for it being applied as early as this to the sea around Malta, but I haven't investigated it on my own, or the significance of the "Typhonikos wind called Eurakylon" (called Euroaquilo in the Vulgate).
Admittedly on general grounds Malta looks more likely, but I don't think it is definitely settled; is there any fossil evidence that poisonous snakes were ever on the island?