I noticed that there's been some kind of entity editing in your single player maps. The "Error: could not find spawn point" message is what you get when you try to load a deathmatch map that does not have a normal player_start entity or a deathmatch map that has no player_deathmatch_start entities. I'd try serving the normal unedited single player.
Gator: The sad thing is that co-op in q2 was really broken, especially in comparison with previous id games. My only hope now is that Paril and the likes throw in some features to make co-op worthwhile and stable.