Yes, this is all true for normative Judaism and Christianity. There's, however, one tiny detail -- for Jewish monotheism to emerge from Canaanite henotheism, it contains too much (sometimes almost verbatim) common material with Vedic Hindusim, material which, however, can be found neither in Zoroastrianism nor other near East / north African religions. And that material is so "low level" that it's hard to imagine that it was retrofitted (it’s exactly what makes Judaism monotheistic). I mention it only because Christianity (no matter its origins) appears to pop up by building upon this thread which is at the core of Judaism (while stripping away a lot of other influences, and then adding their own as you describe).