By the numbers, you're doing pretty well, and I'm not sure how changing masks could cause you to start feeling more tired, given that your leak rates have actually gone down.
Did you start/stop any medications around the same time? Change your sleep routine? I notice you clocked 7 hours on the night you posted; maybe you need more sleep than that?
Here are some ideas about reducing or eliminating mouth leaks. Many people find that chin straps are actually counterproductive, because they tend to pull the jaw back, which makes it harder to keep the mouth closed.
1. Tongue position. Try putting the tip of your tongue behind your upper front teeth. Then position the main part of your tongue up against your upper palate. Finally, give a little suck or swallow to create a bit of suction. You should now be able to open your mouth while breathing entirely through your nose. Practice this during the day, and see if you can get it grooved in deeply enough to help while you are asleep at night. For some people, this is really all it takes to avoid mouth leaks.
2. Collar. If your jaw tends to drop down during the night, pulling your mouth open, then a soft cervical collar, or a firmer snore collar, can be a big boon. More here:
http://www.apneaboard.com/wiki/index.php...cal_Collar
3. Although chin straps tend to pull the jaw back, which is not helpful, the Knightsbridge Dual Band strap has a design that pulls the jaw straight up, which makes it a possible alternative to a cervical collar.
4. Tape. Some people (including me) rely on tape to keep the lips from opening. (I can't rely entirely on the tongue thing.) When the lips open, all too often that eventually leads to a noisy and disruptive mouth leak. To see whether tape would be feasible for you, I recommend that you invest in a box of Somnifix strips. They are very gentle on the skin but hold very well. Be sure to curl your lips inward per instructions before placing the strip. If these work for you, then you can experiment with lower-cost options.
Note about tape: Some people avoid it, for two reasons. (1) If you suddenly need to vomit in the night, the tape could lead to your aspirating some vomitus, which would be bad. However, you can sacrifice one strip to see for yourself how well you can pull you mouth open in an emergency using only your jaw muscles. (2) If there is a power failure and your machine goes off while you're sleeping, you won't be able to do the natural thing and open your mouth to breathe. As for that, out of an abundance of caution, I've put a circuit alarm in a plug on the same circuit as my machine. It will wake me up immediately if I lose power to the machine.
