Go here for publishing info on HL2 Filefront: Half-Life 2 Files - Submit Your Files
Q1: I highly doubt it... Q2: Yes, when it's in the steam games list, right click on it and select "create desktop shortcut"
You can also got to Mod DB.
1. I have created a new mod and changed some of the code and scripts files in it, so it won't be enought just to give other users only the map itself. 2. I do not have my map in the steam games list.