I got some more time to look at this.
If the previous bridges didn't fix, then messing with the tileset might not cut it. So I'm playing it safe and putting some events that will just implement the passability stuff properly.
I'll also have the third fight trigger handled. That'll be an easy fix.
Twister bonus damage hitting through defense is intentional. I imagined it as more of a "status damage" added on to the Deflect.