Goblin Gully

I'm going to be running Goblin Gully for a party of two this week and thought I'd have a go at statting the final creature.

Once the door is open a gurgling, sloshing sound can be heard from below. The pit is home to a putrescent mutant mass of flesh – the last remnant of the Kale experiments. It is treated as a black pudding but is far more terrifying looking as putrescent appendages grow and are reabsorbed. Creatures with less than 4 Hit Dice seeing it must make a save versus spells or flee as if under the effects of a cause fear spell. If they fail to bolt the door, the creature will be free to destroy the town...

Black Pudding
Blending into the dark waters of the swamp, black puddings are predatory oozes that dissolve their prey into basic sustenance.
Instinct: To dissolve, to break down
• Dissolve an unattended mundane item
• Corrode an item, making it less useful (less damage, armor, uses)
• Blend into swampy waters
Level 2, 5 HP, 6 damage

How does it usually hunt or fight?
   All by its lonesome: 9 damage
What's the toughest it's a threat to in its usual numbers?
      A rural keep or guarded neighborhood: +8 damage
How big is it?
   As big as a cart: 25 HP, Close, Reach
What is its most important defense?
      Leather armor or a thick hide: 1 Armor
Which of these describe it? (Choose all that apply)
      It isn't dangerous because of the wounds it inflicts, but for other reasons: -2 damage, write a move about why it's dangerous
      It has long appendages or weapons: Reach
      It doesn't have organs or discernible anatomy: +1 Armor, +3 HP

So, stats so far:

HP 28
Armour 2
Damage 16
Close, Reach

• When you first see the putrescent mutant mass of flesh, roll+WIS. On a 10+ your mind overcomes the horror in front of you and you may act normally. On a 7-9 choose one:
  - You flee from the creature.
  - You stand transfixed by its horror.
  - You run crazed towards it, weapon swinging indiscriminately.
• Dissolve an unattended mundane item
• Corrode an item, making it less useful (less damage, armor, uses)
• Blend into swampy waters

Thoughts?

The monster seems good, but to me the 7-9 results in your custom move feel more like a miss, not a hit. So, i think it should be something like this:
When you first see the putrescent mutant mass of flesh, roll+WIS. On a hit your mind overcomes the horror in front of you and you may act normally. On 10+, you even got a +1 forward against it.
On a miss choose one:
- You flee from the creature.
- You stand transfixed by its horror.
- You run crazed towards it, weapon swinging indiscriminately.

My thoughts were a fail would be a descent into madness (its a one shot game), however maybe that's bit too harsh!