Hi,
3000 POI is a lot for one map, so I’d suggest splitting them into separate maps, for example “northeast” and “southwest” regions or something similar. Enabling clustering may also help with rendering speed.
You can import all POIs to one map, but if you want to have a post for each one, it’s better to create a map with one location for each post using a CSV importer, then combine all the locations with a “mashup” map (available in the Pro version). When creating the posts, you can set a custom field (or fields) to hold the address for the post. MapPress can then generate the maps automatically as the posts are saved.
If you have further questions, please reach out to me at the contact page. You can also get a free demo site, with the Pro version installed, to play around with from the home page.