The headset advice is good. A comfortable set that is nice and clear makes a difference.
As for the fatigue you will eventualy get over it (for most flights). Just remember when you are flying you are far more alert than you usually are, and when you are learning to fly you are trying to learn whilst being highly alert all the time.
Without panicing you it might be be worth getting a carbon detector in the aircraft. Chances of there being enough carbon emissions making it in to the cockpit a fairly low, but it is something to keep in mind.