“How did you come to decide that Timothy in the example and other writings were truly scripture and truly inspired by the Holy Ghost?”
Not its historical validity, its coherence of teachings from one book to the next, its sublime principles and high philosophy beyond that of any man-made philosophy, though it has all of these; ultimately the sole deciding factor was the quickening and revelation of the Holy Spirit upon my own soul.
Mat_16:17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
So your direct personal experience which you decided to trust.
Not that it matters, can we assume that if it were historical invalid and incoherent you likely would not have gotten to this point?