I think the issue with the pathfinding is that once you are adjacent to an enemy, it tracks you move for move. There is no way to get past it, and if it happens to be standing on your lantern, then you can neither recover the lantern, nor attack it. All you can do is move back and forth while it continues to block you.
Is the lamp supposed to have an AOE effect? I've not seen it kill anything other than the target square it lands on.
I can definitely see the light/sanity trade off, but the balance isn't quite right yet. You can't skip lighting torches, because loss of sanity just kills you outright, so you just have to live with the lack of oil.
I assume the blue ghost isn't supposed to be destroyable?