I cant answer your question on the doors, because I rarely use them in a deathmatch map. For one reason or another, they usually worsen the gameflow.
About things breaking once, remember that not every player joins a deathmatch game in its first moments of play, so they most likely will miss that thing/s breaking...
Spawn points should be placed more or less close to a weapon and in places where the player might have a chance of surviving. The central area of crossfire, for example, is one place where you dont want to place spawn points because the player would last 2 seconds there.
Place ammo of powerful weapons away from those weapons, so players move around and dont camp.
Think that not every weapon belongs in every map: A map with narrow halls and sharp turns would work well with shotguns, tripmines and satchel charges, but the RPG and crossbow would be pointless.
etc