For question 1: http://www.bobafamily.com/blog/2011/11/06/how-not-to-hurt-your-back-when-carrying-your-baby-in-a-carrier/
For question 2: http://www.bobafamily.com/blog/2011/10/02/how-your-babys-body-is-adapted-to-being-carried/
As someone who has recently managed to prolapse a disc in their spine even the physio has been recommending that I carry the wee man for a few minutes everyday in an attempt to help fix my back.
oh and if you want to see one of the benefits of me becoming a Boba Ambassador, have a look at the Boba 3g (tweet) in Asian Based Carriers that I was given.