Welcome Swiftshadow.
Although I have little to add to your thought-provoking topic, I thought I'd post in support of your idea that the hobbits were indeed briefly understanding (if only in part) Aragorn's true lineage. I had always read this quote to mean that, although Firefoot's glimpses of other Dunedain is also plausible.
Also, even though Earendil ultimately chose to remain with the Firstborn, I don't see any problem placing him at the end of this particular line. Aragorn's relation to the Mariner is important to his claim to the kingship. It is his descent from Earendil by Elros and the line of Numenor that gives him claim to the Kingship of the Numenoreans in Exile, explains his long life, his fostering in Rivendell, and other important personal details.
Drawing the parallel between Aragorn and Earendil also serves as a mirror for Aragorn's relationship with Arwen. Both marriages were composed of two parties with mixed blood (Earendil the son of Idril and Tuor, Elwing the daughter of Dior whose father was Beren; Aragorn with distant elven heritage, Arwen the daughter of Elrond Halfelven). Even though both couples have less than 'pure' bloodlines they are each considered key unions between men and elves (without Elwing's influence Earendil would probably have chosen mortality). A connection with Earendil, Aragorn and Arwen's mutual forebear, also points out the healed division between Elrond's and Elros's children (a point which is somehow bittersweet in my mind).
So, to sum up, I find Earendil an appropriate choice for the end of the lineage even though he is not technically a Man.
Plus I'm defending my preconceived notion on the subject.
Finis.
Sophia