I leave for two weeks in Japan next week, and so far, so good.
Interestingly, I ran out of cat food last week and was too busy/temporarily broke to buy more, so I fed him real meat: scraps from what I was cooking, canned turkey, canned chicken. I saw a noticeable improvement in his coat and behavior. The mats became easier to remove, and I actually saw him grooming himself. He really has only one mega-mat left, under his chin. It stuck out so far that it was past his mouth and looked like a ruffle.
He had previously resisted my combing his chest and neck, but it was getting ridiculous, so I took out a scissors, held him still by the scruff of the neck, and cut out the farthest reaching part of the neck mat. (For obvious reasons, I didn't cut too closely.) He let me do it and actually seemed relieved.
He still trembles and sleeps a lot (well, he is a cat), but he seems better somehow. I wonder if there's something in even the best cat foods that doesn't agree with him. Next time I can get to the pet supply store, I'll look into raw food diets.