Was it only the respawn points, weapons and objective points that count towards it from the original items or do the original scenery objects count as well?
Everything counts. It's up to you whether or not the default scenery objects are worth dealing with. It's been found that you can safely delete the scenery and vehicles (if you're not making a vehicular map) without reaching the OLN. Where you get screwed is when you delete or lose through co-forging on XBL the starting spawns, spawn areas, and objective items. There are 76 spawn points on the map that count toward the OLN as well, so use them as much as you can.