1)
Did Chiram send only one boat?
1.
Radak: He sent boats 1 , like it says in Divrei ha'Yamim II, 8:18.
2)
What are "Anshei Aniyos Yod'ei ha'Yam"?
1.
Radak citing Targum Yonasan: They are sailors who are experts at conducting [ships] on the sea.
2.
Malbim: Anshei Aniyos are people who know how to conduct ships. Yod'ei ha'Yam are people who know the way of the sea, winds, etc; they are sailors and ship captains.