Great looking rock! I made my rock homemade too. It will take a while for the rock to cover with algae and corraline, but once it does, one can barely tell that it is homemade.
You know by now that the rock is lighter and less dense. This means that there is more surface area and spaces, nooks & crannies for beneficial organisms to live and breed.
As for the amount of rock (weight) per gallon using homemade rock, I do not know a definitive answer. Because of the porosity of the homemade rock and extra surface area, less weight is needed than normal but how much is a crap shoot. I would personally rock scape the tank with what is appealing to the eye and add as much rock as you are comforable with, considering the livestock (both fish and corals) that you intend to keep.
I hope you will host a club meeting soon. I'd be happy to donate sand to seed your sand bed along with crushing a rock I have made to help seed the tank with corraline along with the needed bacteria for the nitrogen process in the tank.
Banker John