Every panchromatic film must be loaded in any reel in completely darkness. Untill the film fixer process has been finished it should be in the (daylight) developing tank. But this developing tank should avoid any light to the film during processing.
Any rapid fixer should be OK. In my case Rollei RXA 1+4 for 6:00 minutes. Any Delta (Ilford) or Tmax (Kodak) film takes a bit more fixer time then a regular cubical type Silver crystal film like e.g. FP4+ , HP5+ (Ilford) or Tri-X 400 (Kodak).What about the fixing time and the fixer? How much time have you used that for?
Take a small snap of film and put it in the fixer (working solution). Make the timing till it is completely CLEAR. You right fix time is 3x the CLEAR time in my case the CLEAR time was almost 2:00 minutes.
I am using a Stop bath (1+19 RCS, based on Citric Acid with indicator) too. It prevents a to quickly contamination of the fixer and the time schedule of an exact developing time (in this case 9:00 minutes) is guaranteed.
When it is going from Yellow to Blue the pH of the Stop is passing 5,5. Then you can put it away and it is finished for the job it did.
Good luck with your next film!