To put a little night cap on this story, My experimentation with salvaging this old acid rapid fixer concentrate, it appears it is just not going to happen. After letting my working mixture gallon sit a few days and settle out, I thought I was home free. I poured off the clear solution , saved it, and discarded the scummy stuff. Guess what? The clear solution I poured off the top, is now cloudy itself in it's new bottle. I recall an experiment my 11th grade chemistry teacher had done by making a supersaturated solution of some common chemical, with help from the bunsen burner. He had managed to mix an incredible amount of some powdered chemical in a little test tube of water. Sitting on the table undisturbed it was nice and clear. As soon as he bumped the test tube, a ton of the powdered chemical reappeared and settled like a snow blizzard.
And so it is as it seems, with this old rapid fixer concentrate. I have an idea I could go through generations of letting the sulfur settle out, and each time it will cloud up again. It still fixes paper, but it's not worth the contamination it will cause to them.