1) That's up to you, actually! If you want to keep those fully in effect, then those can stay in play. However, if that's too limiting for play, it's possible that they aren't as adverse. For instance, instead of turning to ash, the character could be outside, but just extremely weak and display more anemic symptoms, such as collapsing when out for too long; or perhaps requiring to stay in the shade or they'll get horrible sun burns (but not death). You can also use emotions to either help or worsen the effect.

2) You'll have to explain more about Flandre's ability. What do you mean by "destroying absolutely anything"?