Hmmm...
1) Is it proven that making a new character fixes the problem?
2) Why would uninstalling the Creation Kit do anything? The Creation Kit didn't cause a problem for Skyrim - it's Dawnguard causing the problem. Besides, the Creation Kit isn't doing anything while Skyrim is running.
Is Bethesda working on fixing this at all? Other threads I've read seem to indicate that it's Bethesda's memory leak or other technical problem.
To add to crippknottick's comments:
1) Scripts from uninstalled mods may still be running in your current character save and causing problems. The saves for a new character will not have these scripts running. Unfortunately, there is nothing currently available to remove these scripts from saves, so you have to start over. My current strategy is to create a backup folder for my saves prior to installing new mods, that way I can revert if there is a problem. It's a pain, but it saves headaches.
2) Dead on re: the CK.
Are you using any mods that change leveled lists? If so , installing Wrye Bash will help you manage them. In my own game, leveled lists were giving me some problems which led to CTDs. Wrye Bash fixed that for me.
Yeah, something is definitely up with the game--and Bethesda. Fortunately, the game will be fixed eventually. Hang in there. Also, remember this the next time they release a DLC.
You know what you have to do.