i think ebb and flow is definitely your best bet for that number of plants.

the water should wet the rockwool. If you let the water sit for a few minutes the rockwool will wick the water up, so you probably don't have to let the water get that high (though i bet you can if you want).

evaporation: i guess just keep adding more water, or put a cover over your tray.

rockwool: i'm pretty sure this is all you need, though make sure you don't soak it too much. rockwool holds more water than most hydroponic media, so you can ebb and flow less often