[Six-line Wrasse]

1. If you do not detect ammonia after 5 days of your live rock being in your tank, I would imagine it was cured live rock. Cured live rock is already cycled rock. That means you do not have to wait for it to re-cycle like you would be uncured live rock. You should be fine with adding an actual live fish.

2. 20lbs. of live rock in a 75 gal. tank should be more than enough to maintain two small (less than 2") damselfish. This wouldn't be the cause of your fish death. The over-loading of the bio-load which is what would happen with 7 damselfish would however most likely be the culprit.

3. About adding more live rock. Unless you're absolutely positive the live rock is fully cured and you never expose it to air, I would wait until you add another fish. Uncured live rock will have the same effect as would adding too many fish. Get at least 50+ lbs. of live rock in your tank and with an ammonia and nitrite reading of 0ppm and nitrates >5ppm. When you get these parameters you can safely add one fish per week and a half.

4. As for the dead shrimp, you can leave it in there or take it out. I would take the dead damselfish out.