By casting Armament Corps and splitting the +1/+1 counters between the Corps and the Abzan Falconer, John almost guarantees himself the win next turn. You need to break through for that last two damage somehow… and the best way to do so is to overwhelm him with more creatures than he can block.

John’s left three mana open for his Mistfire Weaver in case you try something funny, but it turns out that that won’t help if you’re planning to target your own creatures!

1. Tap two forests, four islands, four mountains and two Swiftwater Cliffs to add (both used as generic mana), and (all but one used as generic mana) to your mana pool.
2. Spend to cast the Clever Impersonator, choosing to copy the Armament Corps.
3. Clever Impersonator enters the battlefield as an Armament Corps, and you get to place two +1/+1 counters among your creatures. Choose to place both counters on the Tuskguard Captain. The Captain is now a 4/5 creature with trample.
4. Spend to cast Force Away on the Clever Impersonator. Because you now control a creature with power 4 or greater (the Tuskguard Captain), Force Away lets you draw and discard a card.
5. Draw the Valley Dasher and discard the Bear’s Companion.
6. Spend to cast the Valley Dasher.
7. Spend to cast the Clever Impersonator again, this time choosing to copy the Valley Dasher.
8. Declare the start of your combat phase, assigning your Tuskguard Captain, Valley Dasher and Clever Impersonator to attack.
9. John can block only two of your creatures at most. The third creature will go unblocked and deal its combat damage to John, defeating him.