One of the greatest substantiations of the Bible is the accurate prediction of the future, which was a sign of a true prophet of God. Those who made predictions that did not come true were considered false prophets and rejected. Scripture speaks much of false prophets and the true prophets of God who spoke against them. Only prophets whose messages were proven true had their message recorded in the Bible.
It is true that some Biblical passages are not entirely clear, and therefore could be interpreted several ways. However, many prophecies are quite clear and provide supporting evidence of the truth of the person who spoke and their words, the Bible.
In a few brief examples, I submit the following:
Psalm 22:16 has God speaking in first person, describing that His enemies would pierce His hands and feet; this was literally fulfilled in Luke 23:33. (btw, Psalm 22 is an incredible first person account of crucifixion written hundreds of years before crucifixion was invented.)
Zechariah 12:10 predicts that God as an only Son would be pierced, which was literally fulfilled in John 19:34.
Psalm 22:18 has God saying His enemies would cast lots for His clothing; this was literally fulfilled in John 19:23-24.
Fulfilled prophecy is one of the strongest supports of the Bible and its message.