Autofocus shouldn't refocus for each shot in a autobracket sequence.. I never have a problem with my HDR images from autobracket even if i don't use a tripod. Photomatix will align the images anyway if you select that option Hope that helps..
You generally don't want the focus or exposure readings changing during the bracket so it is best to prevent this in some way. How you do that is camera specific so you might do a google search on exposure bracketing or autobracketing in the Canon 7D. There are plenty of clever people out there who have figured out how to do things optimally for various cameras (beyond what is in the manual).
Contacting pingallery was a good idea. I love her work and have gotten good suggestions from her.
I don't think so - i know that some soft blurs are done digitally in the software - this is just my basic logic regarding all photography, though. Maybe ask Pingallery ? [link] she is very much into HDR and her stuff is to die for gorgeous