The information you have about amodimethicone's being water-soluable when it has a certain ingredient with it has been proven only to be true when they are in solution. Once it's on your hair, that other ingredient has no effect on it. ACV will have no effect on it. A low-poo should do the trick. L'Oreal Evercreme Cleansing Conditioner would be one that's reasonably priced, and easy to find.

Quite honestly, I just use VO5 Herbal Escapes Kiwi-Lime Squeeze Conditioner as my go to co-wash. It seems to do as good a job as any of the others, and it's incredibly cheap (I think I paid $1.39 at Wally's World for a family sized bottle I've barely put a dent in over the course of three months), not to mention that it's easy to find. Since I switched to that (from Suave Naturals, with occasional low-pooing), I've very rarely felt the need for anything stronger, and usually go months between low-poos.
Peace,
Morgan

Baby Fine 3B, low porosity, normal density and elasticity
CGing since July 2008