question 1 : Yeah a rubbermaid is perfect.
question 2 : No, but not a lot..even tough it's porous, some air we be trapped inside and well...it's a rock.
question 3 : your choice..try different patterns, check if it's solid..play with it to create caves for little fishies.
question 4 : Well when you check LFS they have water just over their live rock containers and it seems to work. There's no obligation to fill your tank completely