(Rime had a -4 penalty to AC because the grit is in his eyes and making his skin itch.  I did not add that to the calculation because it is an AC penalty, not a bonus on the attack.)
Dusty rebuffs the attempt with his AoO (rolled 14), hitting with a claw for 3.  Rime has 10 HP remaining.  Rime is at 40N75E25Z, heading west.
Round 237: Dusty charges to 65N60E25Z and claws again (rolled 20+2=22 for charge)for 2.  Rime has 8 HP remaining.