Here my map with your data, probably some duplicates (I didn't wait for end of loading and call it again).
And as a result I have 20240 placemarks.
You have to set some features for map.
First of all, dynamic loading map map objects
Go to map details, Advanced options tab
* Loading map objects dynamically = jQuery
* Load type = All (for example)
* Buffer size for placemark = 100 (for example)
And enable clusterer
Go to map details, Placemarks tab
* Show placemarks in cluster = Yes
* Marker cluster Zoom Level = 12 (example)
I marked "example" because you can do more fine turning
Buffer size give a count of placemarks with one ajax request to server