Kamikaze co-pilots, Scottish Zombie and Ancient star maps

The kamikaze co-pilots had no idea what was going - I doubt Idris had time to explain what was happening. so, why should they believe that Earth would be destroyed and sacrifice themselves for it? Utter Fraff.... In fact why show Prometheus ramming the Alien ship in the trailer.....what a waste of a surprise! Also, If Holloway was 'fried' for being contaminated why did they open the door for the Scottish Zombie (Grounds keeper Willy!) a moment later? Last, why was the Ancient star maps pointing to a Alien military base/ test centre and not the Alien home planet...I assume, all this time they are waiting for us to wake them up.....so they can destroy us. A bit nonsensical if there are 3 other base ships a few blocks away! And what happened to the remains of the Xenomorphs that infected the pile of 'Engineers' that they found?