I naturally carb my kegs. I use beer smith and it advises me to use 1.96 oz corn sugar to achieve 2.3 volumes. I haven't had any over carbing going that way.
I have noticed with my wheat beers that they tend to have a sulfur smell I'm not sure why, but I suspect that it has something to do with the yeast being in suspension. A quick fix that has worked for me is to purge the keg a couple of times before I pour my first glass and that seems to do the trick.