I d/l'ed the WebKit Nightly Build that was available when you posted, and, although it appears that Apple has made headway in dealing with the Safari Web Content memory leak, I didn't run it for very long...
1. I guess it's a function of the way my system is set up, but I repeatedly wound up with duplicate processes, i.e. WebKit/Safari Web Content and Safari/Safari Web Content, with which I didn't care to deal.
2. Something kept messing with my AdBlock For Safari database in /Users/Your short name/Library/Safari/LocalStorage, almost costing me considerable time and effort. (I'm going to start a new thread about that.)
1. That just sounds like you may have been running both Safari and Webkit at the same time. I don't see multiple Safari Web Content processes.
2. I'll be posting some further notes in your other thread.