The information in the link you posted is incorrect. Just because they proxy the traffic on port 80 doesn't mean they can read the traffic. So if privacy is your main concern you could use a straight SSL proxy.
My understanding (and experience) is that plain SSH does not work over 3G. The amazon proxy checks all traffic for the kindle ID in the headers.
The information here is a good start.
http://openduck.com/2010/11/27/hoora...ng-the-kindle/
I have a pre-patched corkscrew which I have been meaning to post for a while, which takes the kindle ID as an argument. Although I couldn't get it to work with dropbear so compiled the openssh client.
Once I did all that and got it working I realised I had no use for it so lost interest!