As for "The Interface". My theory is that in the original timeline he pressed the button and after the Moment, the Interface went into the TARDIS. Rose later absorbed it and it continued it's job "Ending the Time War". The Doctor even explained that it was the power of a God and should a time lord absorb it, it would become a vengeful god. So why did no Time Lords use it? It didn't exist until the 8th unlocked it. Heart of the TARDIS = rule #1 The Doctor Lies.
In the special, the Interface used Rose Tyler as it's Shell only to discover the Bad Wolf now existed. They are one and the same imo. The ultimate Deus ex Machina that can open Time Locks, zap shit, and mock the Doctor