Google MAP API - mapping app

MAPPING API work needed. We have an PHP/mysql application containing latitude/longitude values for 5,000+ points located across our local area. We need someone with experience to develope a mapping interface for the application that will do the following: a) on startup, the map will show the users GPS location using droid or apple tablet. existing points in the database will be shown as markers b) from the list of points, user click will move map centered at that point at predefined zoom level c) map will have ability for user to move an existing point and save the changes in the database d) map will have ability for user to add new points to table and go to edit screen for that point to enter additional data items. e) hovering on markers will display key parts of the data. We tried doing this ourselves with google maps API and hit these roadblocks... a) displaying markers by coordinates was fine, but not scalable. Became way too slow. needs clustering or viewport management. we currently have 5,000 points but would like to have ability to handle 100,000 (perhaps this link will help [login to view URL] ) b) could not move existing points c) adding new points worked but pointer reacted too slowly and points were dropped in wrong location. d) mapping needs to be seemless with the integration so no reloading every time data screens are viewed. NOTE: points are set by picking location on zoomed in map. we can not use GPS coordinates because they are not accurate enough.