2. This is 5 1/2 years old, my apologies, but I only spent 30 seconds on google:
http://www.boeing.com/news/frontiers/archive/2002/september/i_ca1.html

Pls note that B took the A340 info from the AI quarterly service report. To my knowledge, it is generally accepted within the industry that a quad diverts more often than a twin.

I understand the logic behind the fact that a quad is more likely to divert than a twin. I would however be interested to see sound statistics on the issue, ie statistics coming from the NTSB or the DGAC (if anyone has them).

The statistics provided in your link are, in my view, not satisfactory. You need to have statistics that differentiate diversions because someone is sick on board and SDIF (this is far from clear in the chart you provided).

By the way, for basically the same period, Airbus comes apparently to opposite conclusions http://avitop.com/cs/forums/thread/1850.aspx, but this does not seem any more conclusive.