Prometheus II

Much to my chagrin, I watched "Prometheus" again the other night.  WOS hadn't seen it, and she was reluctant to take my word for it.  The movie does not improve upon additional viewing; if anything, closer examination only raises more questions and further diminishes claims to the film's coherence, either as an art-object unto itself or as a prelude to the "Alien" franchise.  For today, though, I have but two questions:

First [SPOILER ALERT], I have a problem with the "big, heroic gesture" at the end of the film.  You will recall that, at the end, our "ancestor alien forefather" is setting off on a mission, presumably to return to Earth and wipe out the human population for some not-quite-understood reason. Idris Elba as Captain I-Can't-Be-Bothered-to-Look-Up-the-Character's-Name gives his life to prevent the alien's departure, by crashing his spaceship, the Prometheus, into the alien craft.

Now, I GUESS I'm willing to accept the idea that the Prometheus had no photon torpedos or other weaponry--it was a scientific vessel.  Similarly, NASA "never" placed laser cannons on space shuttles (wink-wink).  But wouldn't you think that, if the Weyland Corporation could build a ship that could travel however-many gazillion light years, they would ALSO have equipped that ship with some way to, I don't know, COMMUNICATE with the folks back home?  So that, instead of having to kamikaze into the alien spacecraft, Elba could just have sent a message warning Earth that this craft was coming and to blow it into a million pieces as soon as it showed up?  Obviously, the alien ship didn't have any great defensive capabilities.

My second question, though, is even more perplexing.  Arguably the one interesting character in the movie is David (Michael Fassbender), an android, the latest in the long line of synthetics to appear in an "Alien" film.  Remember, though, that "Prometheus" takes place decades BEFORE "Alien," the first movie in the series.  David is, in fact, the ORIGINAL synthetic, the first of his kind. 
So, here's my question: In a movie that deals with, among other themes, evolutionary progress, how do you explain that androids started out looking like this:

Developed into this:

And finally evolved into THIS:

Can anyone accept the idea that Lance Henriksen represents a higher form of "life" than EITHER Michael Fassbender or Ian Holm?  (Don't even get me started on Winona Ryder.)