Do I need more live rock?

I agree that the 1-2lb per gal is the "rule". Really what it comes down to is the density of the rock. 5 lbs of Fiji is going to be alot "less" rock than 5 lbs of Buna or Tonga branch rocks. I would say use the 1-2lbs of rock per gal for the first part, maybe a Fiji base, then the rest can be based on your taste. I know for my, I have alot of rock in my tank...100 lbs and I think its too crowed...but if it was 100lbs of Buna branch, there would be no room for anything hah.

 

Yes, you can stack up your live rock to hide your pipes just the idea of a wall and lack of caves and holes or breaks in the rock work pattern will hinder the water flow in between your rocks again causing detritus build-up and decreasing gas transfer.

 

As for the Mangroves, I don't think the reverse daylight is needed as long as they receive light during the day in some form or other.
The reverse daylight is for refugiums or sumps containing refugiums used to house Caulerpa, chaeto or some other form of plant life or macroalgae!!!! This decreses the chances of your caulerpa especially going sexual in your tank which isn't a good thing. It basically will result in the same thing as if you kept your tank at a higher thermal temperature tolerance for corals which is 82-87 degrees causing Tridacn's and corals to go sexual releasing gametes into your wtaer column basically wiping out everything in your tank!
As for the mangroves, they will do better grown in a mud substrate which will contain a higher ammonium level which they along with macro like Caulerpa love.

 

The caribbean liverock I got from Drs foster smith, all came in huge flat pieces. It was very hard to aquascape with, and judging by your current aquascape, I think it would be very hard to work with.

I'd suggest lalo or figi, but that's me. Tonga branch would also look cool, if you set it up right you could make it look like vines winding through your rock.