The Landing of Elendil

[Osse]

As we all know, Elendil escaped the Wrath of the Valar and the sinking of Numenor with his sons and seven other ships full of those true to the West. He then founded the Kingdoms of Arnor and Gondor. However, I am a little sceptical that seven ship-loads would be enough to populate both kingdoms, dispite them mingling with those people of (mixed or scant) Numenorean descent that inhabited the western shores of Middle Earth! If we reason that (given the situations of departure hehe) each ship could carry (at most) one hundred and fifty people, that still means that only one-thousand-and-fifty Numenoreans were able to land, and subsequently start the new kingdoms. Of course, the documentation covering the events are rather wanting, and state only that Elendil made it safely to Middle Earth with six other ships and then begun the two kingdoms. Of course, this is dosen't say how quickly it happened, but one can be lulled into the assumption that it happened almost instantaneously. This brings me to another point, if the Numenoreans were to successfully start their kingdoms, at least some mingling would have had to have occured with those already living in Middle Earth. Thus, right from the outset, the Kingdoms of Arnor and Gondor must have not been of completely pure Numenorean blood, and the diminishing of the race must have started almost immediately! Also, what aid did the Elves of Eriador give to the Men?