What could have saved the Fifield and Milburn sub-plot mess would actually not require all that much.
When Charlie starts messing around with his helmet, the threat from those back on the ship should have been heard that anyone taking off the helmet would not be allowed back onto the ship, thus resulting in making the taking off helmets a more interesting plot point. They don't take off the helmets there, because, there'd be a severe punishment if they do.
Also, there was no indication about how limited the air supply was in the suits. I thought it should have been far less than what it appeared to be to also add some drama there... and when Fifield and Milburn actually got scared, they'd use up more air faster, it would add drama, as they are slowly running out of air when running wildly down the corridors and eventually start breathing CO2, which will cloud their judgments and will be a perfect reason for why they get lost and had to stay overnight, there should have been that sense of dread that they may run out of air before morning.
So, being stranded, suffering from beginning CO2 poisoning, running out of air, it will explain their erratic and weird behavior when they find their way back to the pod chamber. They could even at that point decide to take off the helmets, knowing that there is breathable air in the silo, because they'd rather live than die... and that brings the danger of contamination and the alien infection.
So little needed to add the drama back into the piece.