Why am I experiencing listener's fatigue?

I think you need to seek medical attention. Listening fatigue is usaully a mental state, but you seem to actually be experiencing physical symptoms. Also, you should get a sound pressure meter and check how loud you are actually a level you are actually listening.

I would take Onhwy61's advice seriously. Other than an overwhelming mid-upper register (say, ~2-6kHz) that is tiring, the physical malaise you experience shouldn't be there. UNLESS of course, you listen really loud (and 10-12 on the volume can be pretty loud). Keep to average levels of ~78-80db spl max.

Do you have any light switch dimmers or flourescent lighting in or around your listening room? No one is going to hear 30k or 40khz but it will give you a headache and ringing ears in a short time. At the very least try and get a SPL meter and see if you have any ultra high freqs bombarding you. Also try and put some cheap out of the box IC's and zip cord just as an experiment, but use it everywhere. Try the free and cheap first. Good luck.

Vertigo, that would be waaaay too much toe-in for me. Try aiming your speakers at a point behind the listening position that is equal to the distance from the listening position to the speakers (7 feet behind the listener, in your case). If there is enough room between the side walls and your speakers that first reflection aren't a problem, I would try aiming them at a distance twice that far behind the listening position. I realize toe-in is really subjective and depends on room, speaker, gear, etc., but that amount of toe-in would drive me insane...not to mention that pointing the speakers directly at the listener's ear destroys soundstaging in a very substantial way. Try changing the toe-in combined with using something handy like towels or rugs for taming first reflection points and see how it sounds. At least it's easy and cheap! Hope that helps.

you are damaging your ears and it is irreversable...