1. You can change the volume control used in Media Center by clicking the speaker in the upper left corner.
2. If you select the files, you can use Tools → Library Tools → Fill Properties From Filename… and set up a custom naming scheme.
So you would use: [Name] /([Year]/)
This should correct any tagging errors, and you should then be able to select your files, right-click them, and use Library Get Movie & TV Info…
3. You can right-click the library view you want to edit and choose Customize View…
Set rules for file display will let you control what files are displayed.
What I might suggest though, is that rather than looking at a specific directory, you use a specific Media Sub Type ("Movie" for movies, "Music Video" for music videos) and tag your files appropriately.
You can set up certain directories to have a specific Media Sub Type via custom auto-import rules.
4. I'm sure it can be done, but I'm not too familiar with Theater View myself. Someone else can probably help you there.
5. Again, I don't have much experience here, but it's my understanding that these controls are for people that want to replace their AVR with the HTPC, rather than being used with an AVR.