I had a pond that was very similiar and I can tell you that you are on the right track.
Here are two comments:
1) I do not understand why you are not getting a good bloom. I would look into this...
2)We use to catch crappie occassionally on artificial baits. A few years ago, I built some tree reefs out of cedar trees and we started fishing for crappie with minnows. WOW!! I couldn't believe how many big crappie we caught.
And even today, we still catch lots of big crappie. I say all that to say that you might want to sink some trees and start enjoying the crappie fishing.
Good Luck,
DR
