My response is that we Christians (but not necessarily you!) should stop giving air-time to these Muslims who have zero interest in engaging in a genuine discussion. Their only agenda is to generate arguments, no matter how bogus, to distract Christians and to cause them to lose their faith. We should ignore these servants of Satan and recognize them for what they are, which is disingenuous destroyers of faith in Jesus Christ.
But, having given out my rant, let me answer your question. Here is the bottom line. Either the things recorded in the Old Testament are inspired by God or they are not. There is a vast swath of evidence that says beyond all reasonable doubt that, in fact, the writings recorded in the Law, the Prophets and the Writings are inspired by God. This evidence includes many dozens of incredibly specific and 100% accurate prophecies of the future which have come true, both in Christ, and in many other contexts. Add to that the historical reliability of the Bible, the scientific wisdom of the Bible, and the confirmation of the inspiration of the Old Testament by Jesus Christ who was himself raised from the dead, and SO many other kinds of slam dunk proof of inspiration of the Bible–none of which the Qur’an has!!!
Therefore, such discussions are moot. Here is the question: Is the Book of Isaiah inspired by God? Answer: Yes it is. Why? Because God caused it to be inspired. Proof? Sure. Isaiah 53, Isaiah 11:1-2, Isaiah 9:1-6, Isaiah 7:14 and many more. Is the Book of Hosea inspired by God? Yes it is. Proof: Hosea 6:2 and the incredibly foreshadowing in Hosea Ch 1-3. Does it really matter if Hosea had a father who was also a prophet? There were MANY prophets in Israel and Judah, most of whom do not have Scripture in the Bible. So what? How does that affect the central question, which is whether these passages are inspired? This is just a smoke screen. Midrash is not inspired. Whether these Jewish writers are correct or not is up for debate. Either way, this has absolutely zero impact on whether Jeremiah or Ezekiel are inspired, and they obviously are, as the Qur’an recognizes. Is it possible that Isaiah quoted an earlier prophet in Isaiah 8:19-10? I suppose. What does that have to do with anything? This is simply a Muslim trying to create smoke to confuse the Christian believer. Let us do all of us a favor and stop reading stuff by these disingenuous Muslim attempts to destroy genuine faith in the Inspired Word of God, made by believers in a false prophet.