Man, it's gotta be tough for defenders of the literal interpretation of the old testament. Firstly, there isn't much out there to substantiate its historicity outside of its own text, which often leads to "well, how do you know it DIDN'T happen, huh?!!?" Checkmate? Secondly, not only would you have to explain all the absurd parts while attempting to maintain the appearance of a reasonable person, at the same time you're straight up admitting to worshiping a deity that you believe killed thousands of children because their society's leader was a dbag(who was actually about to let the jews go but said deity changed his mind for him so he could commit said genocide).
I think you get to be debate team captain if you can hold your own arguing that side.
Arguing that many of the stories in the OT are based around some sort of factual, historical event does not necessitate believing that they were actually ordered or orchestrated by God.
Also, there is discontinuty between the accounts in Scripture, which leads to the idea that there was some event, but now cloaked in a religious re-telling.
For instance, there is a major discrepancy between the number of Israelites in the Exodus and the census in Numbers. Exodus speaks of the Israelites as a "small nation" and one smaller than all the Canaanite nations. Yet, the census presents the number of Israelite men as 650,000, an incredibly large number. This is either a textual error (as the Hebrew word for thousand can also mean "troop," or fighting group of indefinite number), a gross exaggeration, or a flat-out falsehood.
Historically speaking, the Exodus would have been done by a much, much smaller number of people---perhaps anywhere from 20,000-70,000 peope. This would give greater credence to the fact that there is such a lack of archaeological evidence. Likewise, the typical dating of the Exodus may be wrong, as there is archaeological evidence for a community of Canaanite peoples in Egypt in the 1400s BCE. The destruction of the walls of Jericho also fits with that time.
The movie "Exodus: Patterns of Evidence" gives an interesting perspective on this issue and argues for an early date for the Exodus.
Now, even if a historical event such as the Exodus occured (insofar as is historically "proveable"), it does not mean that the doctrines of Judeo-Christianity are true. Even if a contingent of Semetic people escaped slavery in Egypt, it would not show that plagues occured; or, even if they did, that such was caused by the God of Abraham. That's what I mean by not historically "proveable."
The historical accounts of the Bible can be based in some factual event, yet the doctrines of the Bible can also still be false.