Cont'd from last post.
Re: the drying up of the river Nile in Isaiah 19, the atheist mentions how no record of this is preserved, as if that is some great thing. The Nile isn't a magical river that is always full. During the dry season, it is greatly diminished. Archeology has discovered large jars for long-term storage of large amounts of water, presumably for the dry season, and these would be unnecessary if the drying up of the river was unthinkable. If God prepared some great drought, it could have dried up just as the passage said, and there is no reason why the atheist should be so surprised at this, even from a natural perspective.
Re: the language of Canaan being spoken in Egypt in Isaiah 19, that is symbolic for the language of worshiping God. There is much that is symbolic in Isaiah 19 and anyone can see that by reading it. This is fulfilled in the many Christians who worship there today.
The atheist notes several places where God said a battle would be won, or God would drive a people out, and it didn't happen. This is similar to the Jonah story, in which God promises destruction to the Ninevites, and when they repent, He cancels His threat. There's a similar thing going on in these passages, except instead of the bad guys repenting, it's the good guys who fail to do God's commands. When God says He will do something for you, if you fail to do your part, God won't do it. That's a simple Biblical principle that God had told the Israelites many times, and so they learned by experience that if they didn't follow His commands He wouldn't fulfill His promises. The Israelites were the ones who were responsible for the enemies not being driven out, and not all of the land being given over to them, etc. That means it was an unfulfilled promise, but it doesn't mean it was an unfulfilled prophesy. You have to learn to make a distinction between the two.
Re: Israel living in peace, that is a messianic prophecy and isn't intended to reach fulfillment until the end of time.
Re: David's line lasting forever, that's a fulfilled one: the Davidic dynasty still has its living king, and He is Jesus. He still holds the throne, so the dynasty is still enduring.
Re: Cyrus conquering Babylon, that one happened, it is a pretty well-known historical event, even the atheist admits that it happened and merely says that the writer of Isaiah would have seen it coming.
Re: the messianic prophesies, whether these have been fulfilled or not has always been a point of dispute between Christians and non-Christians. There are lots of Christian answers to the objections surrounding those prophesies, and how not everything in them seems literally fulfilled during Jesus' life; check around for some of those answers and get back to me if you don't find any, but I think you will, they're pretty common in apologetics literature. That also goes with the prophesy about Nebuchadnezzar's dream.
It is interesting that there's almost only two points where atheists think their case is rock-solid, and those Tyre and Egypt. Christians seem to have well-known answers for everything else. That atheists should have only those two as the big buggaboos actually says a lot in favor of the Old Testament Prophets. They have prophetic passages from end-to-end, and atheists can only find two where the apologetics literature gets difficult? That is actually a big testament in its favor. And I find the Christian arguments re: Tyre and Egypt to be particularly strong anyway, so I'm happy to point out the winning nature of the Bible on those two points as well.
Anyway I hope that helps. God bless!