Prometheus Problems

The opening scene - was that guy, er..."guy", supposed to be the initial introduction of life on earth?  Are we to conclude that we, like the Aliens we all know, are also just a different weapon variant from these same guys, the Engineers?

Dr. Shaw, while drugged, hides a baseball bat (or equivalent), which she uses to assault two crew members, drags herself (writhing in pain) to the wrongly-sexed surgery machine, which she expertly knows how to operate - despite the fact that it was established how rare these machines were -  where she has one of the progenitor weapon-creatures extracted successfully and she crawls away freshly stapled.  She arrives in the medical bay where they are reviving the old Weyland - and NO ONE ASKS WHY SHE's COVERED IN BLOOD.  They simply put a towel around her and she starts interrogating more plot out of the new character.  Only David even mentions it, and even that was just a snarky, "you foiled my evil plot", type aside.

Old Weyland is under the impression that the "Engineers" are giving out life extensions?  Hunh?  Why?  Why did he draw that conclusion?  Hope?  Why did he hate his daughter so much?  Because she represented his death?  Her insatiable jungle fever?

Did the Engineers visit all those civilizations on earth and give those coordinates, or were they part of some "return-to-sender" type genetic instruction?  If they did visit, why?  To give us coordinates to their weapon planet...so they could kill us?  What?  When the engineer was revived, despite the fact that David could speak to him successfully, he arose with the single-minded focus to get back to the destruction of earth, after he killed everyone around him - starting with the elaborate (and obviously irrelevant) decapitation of David followed by the simple assault of the non-artificial life-forms.

Almost every single decision made seemed more like whim than anything character driven, and in some cases contrary to their established characters.  Archaeologist who is less interested (IN JUST THE FIRST 6 HOURS ON A NEW PLANET) in the ancient writing and artifacts of the beings which spawned us than in meeting them.  A guy whose whole life was dedicated to studying ancient/dead civilizations?  He was convinced their journey was for naught in a few short hours?  The sacrifice made by the captain and his crew mates seemed totally out of character for them.  How did the captain know this planet was used by the engineers for weapon storage/deployment rather than some other purpose?

"Much nonsense.  Way much nonsense." to quote my Filipino neighbor.  Way much, indeed.