I would consider getting a smaller jug to dry hop in. Hop oils are hydrophobic and will move out into the headspace. Also everytime you take a sample or open the top those oils are flying out.
That's not how it works, oils don't fly. They can oxidize which breaks them down and they do slowly lose their aromatic properties, but the oil isn't sitting at the top of your wort, giving each other a boost to jump out of the carboy when you pull the airlock.