Really glad to hear the CPAP is working well for you. The problems you have are not uncommon.
Oral escape is uncomfortable - and noisey! Have you had palate surgery? Palatal insufficiency can sometimes be the cause of the short circuiting of air being blown in the nose and out the mouth.
Changing the pressure up or down sometimes helps but you must get your attending physician to advise you on this. Some sleep centres recommend full face masks which stop the problem because the pressure at the mouth is the same as at the nose. They are rather large and because of their size the potential for leaking is increased. They are also correspondingly heavier than most nasal masks.
Sometimes Somni Snore Guards are used to block the mouth for those who have palatal insufficiency. Snore Calm Chin-Up Strips are also excellent for this purpose.
Mask air leaks and contact pressure marks are very common and really must be resolved. Getting the right size is very important. There are many on-size-fits-all models around and if you have one of these it may be better to get one that really fits!
You could also try a Nasal-Aire II or an Adam Circuit. The Nasal-Aire II can be seen in the CPAP section. This is a picture of the Adam Circuit (http://www.britishsnoring.co.uk/pdf/adamcircuit.pdf
). Most CPAP users who change from a mask to an Adam Circuit have been very pleased with their decision.
Regrettably there is a degree of trial and error, but the great news is that once you have got your formula right you will be sleeping like a log, not snoring like a hog, and waking up feeling like a new man every moring.