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1) I removed the monster, adjusted the turn, and did everything else. I haven't tried it with a hero yet - I haven't placed it on the map.
2) Size? Hmm. 3x4, but two cells on the sides are like a "slope," so it's 3x2.
Added 2 minutes ago
You could, of course, set z = -2. But I'm not sure. Maybe throw in some kind of rock.
I suggest trying to pass this area with a hero in the game itself. There's a 60% chance the hero will pass normally. Have you tried saving and reloading the editor?