Whirling frenzy and rapid shot both say they give an extra attack per round (rapid shot with a ranged weapon). I can see how rapid shot might need to be made with "the same weapon" but technically combining those with quick drawn daggers should work. Whirling frenzy, at the least, should work.
I know there's an official ruling somewhere that states EB's can be sneak attacks if they're within SA range. I think it's in the weaponlike spells section of CAr.
The unlimited dagger item only works once per round I believe. Yeah, because it's activated as a swift action.
Nice, as a last resort/buffer for my own supply.
The reason I suggested Warlock/DfA was to get darkness at-will. the EB/breath weapon was the icing on the cake in that situation.