Well, I like them!
For feats, would we want Imp Bull Rush or Ability Focus for the Vortex Maw? I'm sort of at a loss for feats otherwise.
We may want to swap Alertness for Skill Focus (Spot).
Switch Great Fort out for Blind Fight or Power Attack?
Great idea! Combat Reflexes it is!
I think I'd make it CR 6, but the rest sounds good.