1) & 2)
For some reason MC13 didn't automatically find the same DirectShow filters that MJ12 uses.
- Go to Options > File Types > Audio > AIFF
- Set the Playback Method setting to "JRiver audio engine (using DirectShow filter)"
Because of the above problem the already imported files have now wrong Media Type field value. You can find the files either under the Video category or under the Documents category.
To fix the latter you could do:
If you already have file data in MJ12 you can create a library backup file in MJ12 and restore it in MC13. (File > Library > Back Up Library / Restore Library). This will work if the filepaths you have in your MJ12 library are correct also for MC13. The restored library will contain all file data you have in MJ12 (the current MC13 data will be replaced.)
or
Fix the Media Type field values. You can find some instructions here:
http://yabb.jriver.com/interact/index.php?topic=50621 (check the last six replies or so).
or
Clear the library and reimport the files (File > Library > Clear Library). You may not want to do this because all file tags will be cleared.
3)
I don't know, but it could be a display driver issue. Theater View uses 3D graphics.