You Got His Attention

Taking the 5 foot step would not be enough for the rogue to flank the Gator in this round, but the Gator shifts himself as well. After taking the bolt to the back the Gator shifts himself and does a tail slap attack instead of a bite.

The Gator snarls, distracted from kaspar for a moment, and its heavy tail slams through the air as it looks back at the sorcerer.

Rolled a 16, and that's figuring in the bonus and the flare penalty. You're crunched.

Castille takes 10 points of damage. He's at -1, so he's unconscious and down. He will lose a hit point each round unless he stabilizes on his own (10% chance each round), or gets one point of magical healing, or receives a DC 15 Heal check.

In the meantime, the Gator shifted to tail slam the sorcerer, exposing itself to a flanking (i.e. a sneak) attack from Kaspar. (Note the DM is not tweaking the rules, there are different interpretations of flanking, and for this round Kaspar is still flanking.)

Your move.