(1) I want to download songs playlist-by-playlist.
Can't you accomplish that by plugging in your iPod to the computer, going to the Music tab, Check the box "Selected Playlist, Artists, etc...", and then scroll down through your playlists list, check the ones you want to sync, and select nothing else?
I don't want any single songs to be downloaded at this time...
If I delete a checkmark with COMMAND and click, ALL checkmarks are deleted, including the ones on the songs in my Playlist.
Are you are concerned that you're seeing your iPod list the songs within the Playlists view AND in the Songs view??
Whether you are viewing a song in a Playlist, or in the Main Library list view, it's the same file, is only exists once on your iPod and or your iTunes Library. The Main Library listing is just a reference of all the songs that are in all the playlists on your device. (Visa-versa actually)
If you uncheck a song in the Main view, it also unchecks that song in ALL playlists... it's the same file.
#3. Only if you have the preference checked on the Summary tab under Options "Sync only checked songs and videos"
#4. Only if you have "Prevent iPods, iPhones, and iPods from syncing automatically" unchecked.
#5. That is where you decide if you want the iPod to sync automatically every time you plug it in, or if you want to manually initiate the sync.
I hope this helps
bd