I use 1% to 2% Acetic Acid as the stop bath for RA4. I have also used Kodak Indicator Stop. Both work just fine.
If you leave out the Sulfite from the Acetic Acid, then the Stop becomes an indicator bath turning cherry red when it becomes exhausted. Adding Sulfite will NOT regenerate it but will decolorize it thereby giving you no notice of exhaustion.
If you bleach in most Ferri bleaches, you rehalogenize the Silver as it oxidizes and this Silver salt is light sensitive. As for using a fix, it depends on the fix. The fix baths used for color processes are selected to prevent shifts in dye hue due to pH. Also, just fixing makes a print darker and less saturated and therefore harder to evaluate.