Outlook 2011 reports incorrect font size
As far as the difference in versions of outlook, MS actually has an official statement about that:
http://support.microsoft.com/kb/2783553

Summary
Email messages that are sent from Microsoft Outlook for Mac 2011 to
other operating systems may have with a different font size than the
original email message font size. For example, when text that has
Calibri font size 14 is sent from Outlook for Mac 2011 to Microsoft
Outlook or Outlook Web App, the text may be displayed as a font size
other than 14 when the message is received on the other operating
system.
More information
This is caused by the pixel-to-point or
point-to-pixel conversion that happens between the Mac and Windows
operating systems.

In other words they're using points in OSX and pixels in Windows.