Jim, you seem to be almost contradicting yourself here. In fact it is by no means certain that there were separate Hebrew and Phoenician languages at the time of the Gezer calendar (9th century BCE? - from memory). At least they may have been no more different than British and American English. They did gradually grow apart. But at the start they were one.
At that time indeed they would *likely* have been close enough to be considered mere dialects of each other, depending on how you define a dialect and how you define a language.
The Gezer Calendar is something that some scholars have fought over rather futilely as to whether it is written in Phoenician or Hebrew or some other related language/dialect.
See http://lists.ibiblio.org/pipermail/b-hebrew/2000-February/006723.html for a summary that I think fits recent tendencies to let such matters lie.
Jim Allan