Not sure why you are having indexing problems. I use an identical set up on at least two bikes and have no problems in shifting. The hidden click is very noticeable and shouldnt slip, in fact the shifting should be like a gunshot on a quiet day.
*EDIT:
Looking at the mech, your top jockey wheel may not have the 1.5mm float of the original. I would also try the mech without that pulley.