Yes, it helps very much. I do see where you are coming from and indeed there is a lot in the Bible that is known to be fact, and yes, one can point to these facts to validate the whole (Bible). I believe the athiest uses the Bible to point out what he sees as inconsistencies within its parts, thus bringing the validity of the whole into question. To me, that also makes sense.
But, in my mind, Christ's arrival as proof of the Bible's prophesy of Christ's arrival is flawed. My understanding is that God promised mankind a saviour, but did not specifically say it was Jesus Christ. Thus that prophesy cannot be proven to have come true.