pH is at the high end of acceptable. The sock and cotton balls was brilliant! IF you can get the rust out via the filter and vacuuming do so. If you have to use a "garden hose vacuume" with a bag, fill it with cotton balls again to catch what it can. That's a gadget called a Slime Bag that does what your sock does, only better. You want to get as much rust out of the water and into the filter or to waste as you can.

If all else fails you'll have to use a sequestrant, a liquid that dissolves the rust and keeps it in suspension until you drain your pool. I've never used one but we have experts on that around here.

Carl