I don't know if this helps, but most people have to try a few different CPAP masks before they find one that's really comfortable for them. This is pretty much the normal usage pattern, and most insurance that covers CPAP at all also cover multiple masks, so I don't know why doctors don't push it more.

For the record, there should not be any air hissing out around the edges of your mask. If there is, you either need to get a different mask or at least adjust the straps on your current one. My experience is that full-face masks absolutely don't work with a beard; a nasal pillow mask works much better, but I do need to keep my mustache trimmed short or it chafes a bit.

Also, I don't know much about the allergy angle, but you're theoretically supposed to change the air filter regularly; there might be filter options designed for allergy sufferers.