Regarding the Ch increase: some days ago, I got an Ap increase completely out of the blue. Was walking through a corridor and "Your looks improve" appears. Ap was 8 from the AMW, and I didn't have the Athletics skill. I would believe it's just a coincidence.
All items that grant resistance to an element are immune to item destruction caused by it. So red clothes and red daggers will never burn in the ToEF, for example.
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Self-flagellation can cure sickness. Any kind of whip will work. Of course, it's a bit unwise to damage yourself under a condition that halves your HP and regenerates it much slower, but as a last resort measure...