Lime has to be really fine to affect the pH much but lime raises ph (at least in acidic water/soil). Our native soils are around 5.5 pH and we use ag lime to bring them up to the 6.5-7.0 range.
If you can get more of the limestone, you might want to dump some piles along the bank in shallow water. The fish like it and will nest in it.
I don't know what else lime does for the water but I think it is pretty hard to get too much of it. We have the opposite problem here (pH being low and needing to raise it) so can't help you much but I'm sure others will have better info.
Looks like things are coming along well. We also enjoy feeding and watching the fish.
