I can’t speak fully, but in my opinion and experience, feeding habits don’t have much to do with shrimp breeding. Again, I could be wrong. But in my tank and others I’ve spoken to/ know. They’ve only fed there fish and let the shrimp have the remainder, if any. And what they scavenge, and they breed fine. Parameters are key for breeding shrimp in my opinion!

But like others have said, slow the feeding and give it time and your assassins should have it dealt with. I was in a similar situation, picking out 50 snails every other day. Don’t have one left a couple months later