– Kerry moved to Coastal Division 13, Cam Ranh Bay
The above info from Kerry's website, combined with your information, would indicate that it is highly unlikely Kerry was in Cambodia on Christmas 1968. They claim he was in a firefight 12/24/68 without specifying the location.
All this may be moot, anyway. I can't find any evidence that he actually made the statement attributed to him in this article.
Your maps are great...I just happened to have been at both places Kerry was...just a couple years before he graced everyone with his presence. I was on the 17th Swift Boat crew to be deployed...pretty early in the program.