1 Numbers next to the stars tell how many different "locations" have it.

2 Stars an indication of confidence of being successful, not an indication of the file's quality.

4 Connection to supply was interrupted

5 Nope --- other than experienced guessing based on file size and bit rate ---

6 Launch gives you a peek at a partial download so you can "test" it to see if it is really what you expected.
Resume forces a connection retry (I bet that was for those 1 and 2 star downloads)

7 Bottom left dot should show green with a number showing the number of files you are sharing. You can look under the Moniter tab to see if anyone is using your source.