Dynamics such as physics can lag source in excess amounts, or with complicated setups. In deathmatch, due to the gravity gun in HL2DM, you need to make many physics props of varying size - Monitors, file cabinets, desks, or cars are all useful and can all be physics enabled.
Place your cubemaps where areas of light and dark are conflicting or transitional. You usually need them under strong light sources as well.
I think what that quotation means is not to use single omnidirectional lights to fill a room with light - Rather to plan the lighting as it would appear in relation to light props and natural sources. Source supports a lot of lights - You can use an entity to cast light for each source, probably, as well as extra lights to fill in areas and to fake bouncing and reflection (dm_steamlab uses this technique a lot.) I'd stick to light_spot entities for the time being, unless you have a specific need to utilize omnidirectional lights (Don't get me wrong, they are useful in some situations) but spotlights are much more controllable and flexible. I generally utilize spotlights and use omnidirectional light entities with lower brightness values to create a colored light wash to lighten up the area.
There are entities for each team's start points and their presence delineates a TeamDM map. (these entities are called info_player_combine and info_player_rebel if I recall correctly.) It will interpret these to mean that it is a team oriented deathmatch map. Regular DM maps just use info_player_start/info_player_deathmatch entities.
Also, a hint - If you're having trouble with measurements look at the /dev textures. They're all properly measured and will fit exactly on their appropriate surfaces at .25 scale if your object is scaled properly in the editor.