The preview of the Curse lasts for perhaps thirty seconds to a minute but no more than that. It is accurate as well, at least if they are Cursed during this period of exposure.
The disruption of magic completely breaks any minor enchantments. Larger spells would likely be damaged but would still be active. The World Bell was disintegrated because it channels magical force into itself. There was just too much for it to contain.
The magical wave strikes Metamor only a few minutes after midnight on Dec 23.
Madog is a strong enchantment so he'll be okay. He'll probably won't be moving for about an hour afterward, and then a little sluggish the next day, but otherwise he'll be fine.
As for divine/hellish magic, I expect they will stay out of the way as this thing comes barreling through. Marzac has been scaring the dickens out of them for years, so much so that none of them would go near it. They aren't going to want to be in the way of the blowback.
I hope that answers your questions.
Dominus tecum
