Also 3% CO2 is not toxic where you'll last only a few minutes... but you can survive hours (or days) ... you may have chest muscles fatigue/dizziness/headache though but not death.

Only at exceeding 5% is where it's truly toxic.

^5 sec google search.

A simple O2 generator/filter from the 21% O2 environment just to increase the O2 percentage and they can stay out as long as they want. Ordinary or simple gas mask will do. Pandora (Avatar's) environment was even more hostile.

Again poor writing without research.

I'd would not say bored.... It just makes it less enjoyable.... Avatar and Avengers were great....

actually a lot of us presumed the beginning sacrifice scene to be giving life to humanity.

ridley didn't imply it was earth (he did say it could be anywhere in the galaxy)

we don't know IF it was a sacrifice was for the creation of life, what we did see the giant engineer drank the goop, fell into the waterfall, he then appear to disintegrate, stands of the DNA appear to break up, and appear to become something else. what else? what IF it was other what we, many of us presumed (mankind)? 

while ridley/lindelof did say the engineers probably created up, in the movie, shaw showed us we share the same DNA, but for not the sacrifice itself did not lend to more then the young giant engineer 'died'.

Ridley did say the engineers travel thru space, somewhat like a gardener. still, it's open to interpretation.