What's the size of the tank? If it's less than a 55g, I would think that that's enough light for Java moss. I've had it survive in a pretty dark tank with no light over it, only ambient room light in a fairly dim room. I don't know what the requirements of an algae wall would be, and I didn't know that anyone would like an algae wall. Then again, maybe you're talking about something else, lol.
Anyway, I have no idea what the GH and KH levels should be, since I'm not that experienced. I have pretty low maintenance tanks and don't really need to worry about that (that I know of, lol). The pH might be a little high for optimum growth of plants, since many grow best in closer to 6 or 7 pH, but I don't know if it is too high.
I've noticed some of my Java moss looking pretty brown, but it is still living and even spreading. I try to tie it down when I can, but sometimes there are threads or sections that get loose and just float about. Some people actually use it as a floating plant, so I would think that it getting loose is not the factor that made it turn brown.