Hello and welcome to MobileRead.
When emailing to your kindle, use
xxx@free.kindle.com rather than
xxx@kindle.com. Also, in the "manage my kindle" section of your Amazon account, set the document charge limit to zero. This will keep you from being charged for anything.
As far as the Calibre issue, there is a specific Calibre section on this forum where I'm sure your question will be answered right away. Just post there and many helpful people will come to your rescue.