this belongs in help.
Each of the things you are looking to edit is in modeldata100 of every stage, StgPosition. For editing boundaries, you want to change the position of CamLimit0N, CamLimit1N (how far out the camera will move) and Dead0N and Dead1N (death boundaries). Spawn points are also bones in StgPosition, named Player0N, etc. I suggest editing each of these in brawlwall, you will be able to see exactly where the boundaries are, and where the spawn points are in comparison to the collision data.
http://www.smashboards.com/showthread.php?t=260800