Steel wool will work to remove silver from all fixes, and the standard tests for silver retention and exhaustion will work as well.
As for running tests, you see how hard, expensive and time consuming testing films and fixers are. Literally millions were spent at Kodak to come up with these formulations with all the tests mentioned above and more. You see, everything mentioned here plust image stability and image structure were tested with exact quantitative measurments to determine the results. Somtimes it took years to get approval for a new fixer with the results being peer reviewed in-house before release. And, it was done by two groups to avoid bias. The originating engineer had to run these experiments, and then they had to be duplicated by an impartial engineer in another group. Then the results were compared in a peer review.
That is why I accept prepackaged chemistry. It takes the burden off my shoulders. If I do make a new mix, I test it before I use it.
But, an interesting observation has grabbed my attention. All of the 'staining' processes are doing is creat a pseudo dye in the coating around the silver grain. This dye blurs the grain, but can also detract from sharpness. But, my point is this, or rather my question is this. What is the stability of this pseudo dye? What will happen to 'stained' negatives over time. Does the pyro induced coloration fade? It certainly fades or is bleached in acid sulfite fixes. Is it not fair to assume that the stain/tint/dye is less stable than the silver and will change over time?
I just wonder if anyone has run that type of test. Because, if the dye is not stable, then all of this discussion about staining developers is moot.