Max chlorine in vinyl pool?

[fade2_blk]

Hi all, could use a little help. Here are my specs:
(Taylor test kit)
24,000 vinyl in ground sand filter 24/7
FC-7PPM
CC-0
PH-7.2
CYA-~20PPM
ALK-150PPM
I have been fighting white cloudy water, which I believe is a calcium cloud. I have been having a lot of trouble getting the chlorine levels up until yesterday. Chlorine is provided by trichlor tabs in a floater and bleach(5.25%) or carboys of 12.5% from the pool place. I understand that chlor and CYA are interrelated and have been looking at Ben's best guess chart. My first question is how much chlorine is too much for a vinyl pool liner. I remember reading somewhere never to exceed 8 PPM in a vinyl pool, is this true? Second is it true that lowering the PH help the chlorine kill algae? After 3 days of rain it is now sunny and hot and the water is trying to go green on me. I have been vacuuming to waste, but it is very hard to do a good job when you can't see what you are doing. Any help or advice is welcome, thanks.