Once you get through the guide posted above, you can install a bloat free rom. I recommend CM9, which is also on the xda site. Ice Cream Sandwich with no A T & T or Samsung mangling. Titanium backup should not be used to restore system stuff, details are at xda. The only thing I use Titanium Backup for is to freeze an app that I think may be "acting up." XDA users will insist that you refrain from asking questions that have been asked a million times already, so search for your answers over there...
PS. Most of the custom roms have no need to freeze a tethering manager app, it doesn't exist. But AT&T won't like it if they find out you're tethering. There are ways to avoid detection, mostly by only tethering other mobile devices.