Tums-
Others can tackle #2-#5 with more better experience than I can offer, but I am absolutely positive that the LMB will be able to spawn and recruit very successfully in a 3acre pond as you describe. I base this on several years experience with a 3 acre, blue cat heavy pond. I'm not suggesting a positive or negative net effect--but it will be different after you add the LMB. Once you put them in, only way to get them out will be to drain and nuke the pond.
If you want more predation, consider HSB?? If you stock some and feed them, they'll grow like crazy to a size where they can have an effect on BG, though they won't control biomass like LMB can.
Hope this helps.
