No he hasn't, which simply invalidates your next statement. It doesn't matter that something doesn't make sense to somebody, if there is evidence validating the theory, that is all that is needed. If I say that I can't make sense of why 2+2=4, doesn't make the equation and it's answer invalid. All it means is that I can't make sense of it.
The Beginning of Time - This lecture is the intellectual property of Professor S.W.Hawking.
http://www.hawking.org.uk/the-beginning-of-time.html
You are wrong. Did you even read it?
Here is the relevant part:
"Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them. This kind of beginning to the universe, and of time itself, is very different to the beginnings that had been considered earlier. These had to be imposed on the universe by some external agency. There is no dynamical reason why the motion of bodies in the solar system can not be extrapolated back in time, far beyond four thousand and four BC, the date for the creation of the universe, according to the book of Genesis. Thus it would require the direct intervention of God, if the universe began at that date. By contrast, the Big Bang is a beginning that is required by the dynamical laws that govern the universe. It is therefore intrinsic to the universe, and is not imposed on it from outside."
From an operational point of view, he now says "events before the Big Bang are simply not defined because there's no way one could measure what happened at them." That's very different than saying that time actually began at the Big Bang, which was his position twenty years ago.
As to your second point, of course it's true that it is scientific evidence that counts. As Hawking says in the very lecture you cite, there is no way to know scientifically what, if anything, existed before the Big Bang. There is no evidence in this case.