3E material is allowed?
You should be getting Craven
and Staggering Strike
If you plan to be stealthy, you will want Darkstalker
If you somehow have the charisma for it, Imperious Command
will make foes you demoralize cower. If you can somehow do that and still have your turn before it wears off, the PF Dastardly Finish feat will let you coup de grace (and you can use Blade of Mercy trait and PF's Enforcer feat to not need to spend an action intimidating), but that's probably beyond your capabilities / feat budget.
Try to get very high CL potions of Greater Magic Fang and Stoneskin (must be from a Summoner) to use with Alchemical Allocation.
EDIT: Wait, 3E! Get a potion of Heroics (from spell compendium) to use w/ AA!