For Judaism, it's not an argument to say Egyptian religion predates it. Ra and Osiris is for another religion. Judaism was translated into many languages, and others changed it. Nobody can really prove that the Sumerian religion came before Judaism, except with carbon dating, where things like to age several billion years/month after a point. That is an argument I've had, so yes, good point.
I don't recommend your arguing about carbon dating unless you have a good reason and lines of reliable empirical evidence as to why you don't trust it for that purpose.
They say they can date it through the context of the writings. In the sense that there are common elements shown in different versions of the same stories, slightly altered between cultures. Some say that these stories were taken and changed to show glory to the Biblical God instead of the pagan ones.
I don't debate along the lines that I can prove G-d. Simply that in thousands of years, nobody's disproved a letter, so you can't say that it isn't perfectly reasonable to be Jewish.
It's not their job to disprove God. You can't disprove something like God any more than you can disprove the invisible unicorn. There is, however, a lack of empirical evidence for either. Because of a concept called Occam's razor, the atheist sees it as logical to take the simple position that because there is no evidence, there is no reason to believe that either exist.
In order for them to accept God's existence, they would need to see some kind of evidence for the positive existence of God. As a theist (someone who believes in God), if you want to argue that such a belief is rational, then it is you who must present this evidence, or credible arguments in favor of your theism, if there is any to present.
Those other arguments prove nothing. I need points that people say disprove Judaism outright. I can disprove any other religion under the sun, but not Judaism, which is a major reason why I stick with it.
Be prepared to argue for the historical reality of the Exodus. This has been called into serious question in mainstream archeology, and yet it is very important to Judaism.
Be prepared to explain why bats are referred to as birds, and why some insects are referred to as "four legged insects".
Be prepared to explain why the Bible seems to indicate that pi is equal to 3, in 1 Kings 7:23.
I have no intention of proving G-d's existence. Atheism can not explain where things began, so it can be disproven like that. It's incomplete. This isn't a religious debate, but a debate for the survival of Israel.
If I were an atheist I'd tell you that our universe was a quantum fluctuation, an errant bubble that arose from the multiverse's otherwise steady state overall.
As for Israel they will not likely be moved by claims of ancient historical presence of Jews in Israel, and especially not by any religious claims to Jewish right to the land.
Perhaps your best bet is finding quotations (with references) from Arab leaders themselves that there is really no Palestinian people.