Every once in a while, it seemed to me, the writers made a point that the Doctor can not just bounce about and do as he darned well pleases. Thus when folks say "But now there is no data on him in all the computers! He must have changed history!" I shake my head. He didn't have to change history. He just had to erase data. Frankly, I think we can blame Oswin. And who knows, perhaps rather than the Doctor erasing all that data, Oswin did it when she wiped the Daleks. For they also are time travelers. Now, instead of a "That's the Doctor, and this is the Doctor, and that is the Doctor!" the Dalek records have a "We encountered this annoying humanoid. And there was another different one. And there was another...." They have no reason to connect the events. So, I can postulate that members of UNIT remember the Doctor, but they don't have data in their computers any more.
The Doctor only once tried to mess with a fixed point. The woman involved killed herself in order to undo the damage. Thus he has accepted that there are limits, and he is not going to destroy what cannot be restored in a vain effort to defy them.