In response for item 2 on you request. You can use the bpflist command to see what files were backed up, well use your clientx as an example.
bpflist -client clientx -d 12/04/2007 00:00:00 -e 12/04/07 23:59:59 -rl 999 -option GET_ALL_FILES
I usually pipe it and add an awk statement of awk '{print $10 }' so that I get just the filepaths backed up.
This does not give the media id used for backup but you can get the list of files backed up form the previous night.