The Doctor doesn't consider Gabriel dangerous, unless put in a dangerous situation. Though it's probably wisest not to piss him off. But the Doctor isn't always considered wise.

"And I you," he agrees, hugging her tight. They both know that they would be better off with their respective universes' versions of each other, but there's not much to be done about that. Obviously he doesn't need Rose or Donna or anyone and he's not at all upset about finding out certain things from the metacrisis earlier.