-Why was the engineer in hypersleep for 2000 years when he could have just taken a ship to go to his relatives?
This is very open to debate... and the deleted scenes change the perspective of this..
The Engineer went into Cryo-sleep to escape the effects of the Outbreak is the most likely cause....
Then we just dont know, if he had a say Alarm Clock that never went off and so he overslept... or if he had been waiting for others of his Race to come to rescue him?
The Deleted Scenes add up to maybe did this Engineer have a change of Heart and did he Sabotage the mission?
Indeed surely they would know the Half-Life of the Black Goo and so would know how many years to stay in Cryo-sleep.
If this is the case, and his intentions was the same, he could have left LV-223 at a latter time and carried out with the Mission, or even returned to the Home-world and explained what happened.
A lot depends on his Agenda and what side he is on...
Did he perform a Sacrificial Act to prevent the Mission and then kept himself locked away.
It seems the re-shoots and Plot Ridley was now going for was that these beings are simply Nasty and not Benevolent and he simply Went into Cryo-sleep and never woke up.
The Hologram seemed to show they was getting ready to leave and go into Cryo-sleep before things went to POT...
Spaights draft showed a extended one, where David fast forwards the recording and then we see One Last Engineer who was rushing around and Panicking.