Okay..so you are saying the map is very laggy itself? Sorry, I got lost in there. x3
The best solutions I have for you is turn off the water reflections and the nametags, lower the resolution, etc.
Hope everything works out for you in the end, bud. ^^
I just have a few questions.
First off, are you using meshes from the game itself or meshes that you've downloaded? If so, is the collision on 'Own Collision?' This can make meshes a lot more laggy than they need to be.
Also, before you start the other's suggestions, BACK UP YOUR FILES.