On the fisrt issue. Depending on the types of coral you want to keep 10x/hour is a minimum for shrooms and leathers and some LPS. If you are wanting to keep SPS 20x/hour is a min. My tank is near 30x and I keep a mix.
Second issue. For a tank that size you have about the min of live rock that I would uses. A little more would not hurt, but is not necessary. As for the sand If you are going with a DSB you will probably need a little bit more. I have 110 lbs in my 48 x 18 foot print tank and that give me roughly 6" of sand bed.
Third Issue. I would ditch the balls. If you want to add liverock rubble do so just where it will be under water all of the time. Check out hirocks.com you can get 30lbs of base rock rubble foe about $30 shipped.
I would suggest a closed loop or a tunze stream or like device. If the tank is new get it drilled if not go with an over the back closed loop. From my loop I get about 15x, about 8x from the return pump and the rest is from 3 MJ 1200's and 1 MJ 900. Keep the powerhead they are good at hitting dead spots. IF the sand you already have is live try to find some southdown play sand it works just as good as long as you have some seed stock. Or there are more options for dead sand that will not cost a fortune. Also save a few bucks and do not buy any live sand in a bag. Most do not have much live in it buy the time we get it. Get a cup here and there from some local reevers or you LFS.
