seems to me you're seeing the mental health of the cat. when a cat is chewing / scratching everything in site, then they don't have enough to do. outside cats have to be outside, keep them in and you get neurotic behavior. some cats really are ok inside, they won't claw.
the first thing i think when i hear of a cat needing to be declawed, is that they need.... a porch. even if they can't go out, just to sit and watch nature and have alittle sun at their backs -- seems like this could do the trick. don't know if i'm right about this. i mean, i go stir crazy if i don't go out, either.
i'd never get a cat declawed, no matter what. not unless i went to the doctor and had my nails cut off first. (really, that's just what it is).