1) Indus Valley civilization as the entry point of Indo-Iranians (i.e. Indo-Europeans aka bearers of Sanskritic Vedic tradition) into Pakistan and Indian Subcontinent. Maybe not the most correct way to phrase it, but I'm sure you get the point. Anyway, that culture was around 1200 BCE definitely familiar with monism (as you call it).
2) As for deserts -- please make the effort to look into atlas. There is whole (already mentioned) Indian Subcontinent between Middle East and China and it's far from being a desert. This is elementary to high school stuff.
3) I'm sort of glad you ascribe cannabis merely coincidental role as it gives my argument even more weight -- you have huge desert (Gobi - half the size of Arabian desert) in Mongolia and China with pretty lively nomadic population, yet no native/local monotheism, the same with Uzbekistan and Turkmenistan (Karakum - though not as big as Gobi). One may argue that those deserts are cold, but again, in North America and Australia you have pretty big subtropical deserts (the same type as Arabian desert or Sahara) yet still no native monotheism. But first and foremost, the monotheism (Atenism) in Egypt was more or less a very brief anomaly (few decades IIRC), was never universally accepted (as in all of Egypt), and the whole Saharan region (three times larger than Arabian desert) had no other known example of locally emergent monotheism neither before nor after despite the plethora of various culturally distinct tribes inhabiting it.
4) Well, the Jewish tradition itself states pretty clearly that it got its ideas from Mesopotamia (Sumer and Akkad, specifically city of Ur). The actual description of what Abraham went through (meeting with God) then very much resembles some mystical experience (either pure hallucination or, more probably, seeing God in those visitors which is pretty much an archetypal experience on the path of non-dual understanding).
5) As for the religious experience of an average monotheist, I would say it was the same as the average experience of an average polytheist. After all, every monotheistic religion is dualistic and has a pantheon of "celestial" beings and is merely a variation of polytheism. Heck, even the first name of God mentioned in Tanakh is plural Elohim (i.e. "children of El"). So it boiled down, as is the case even today, to dumbed down knowledge / dogma, and going through the ritual motions -- with no actual experience or realization.
6) You seem to have a hard time distinguishing between monotheistic religion and the non-dualism it is built upon. It's not core of monotheism that I'm talking about, but core of what you call monism (aka non-dual understanding of reality). That being said, you can't be seriously asking how is Judaism similar to Christianity, when substantial portion of alleged quotes of Jesus directly cite or paraphrase Tanakh all over the place, with special emphasis on, and explanations of, the aforementioned non-dualism. See e.g. John: "I and the Father are one"; "Before Abraham was, I am"; "I am in the Father and the Father is in me" (all references to Exodus 3:14 and/or Psalms); or explanations in Luke and Thomas that Kingdom of God is simultaneously within and without (themes that can be found in e.g. Jeremiah); and many others.
7) Are you trolling me? It very much feels like it. That is, if I give you the benefit of doubt, that you are actually not pathetically uneducated. Anyway, I see no reason to continue with this fruitless back and forth. Bye.
