The AAM 11.5 is very reliable and not picky about brand or grade. Needs a bit of FM for the clutch pack if G-80 equipped, which this one is.
Diff fluids see far more Fe than others samples like engines. This one is perfectly fine. Nothing but expected normal wear here.
As for the OCI, one or two drain/fill cycles are all that is needed and then 100k miles thereafter if using any decent syn GL-5. No need or benefit to overly frequent changes, as they won't alter the wear rates. Jim Allen told me in an off-line conversation that diff gear wear is about 99% attributed to gear/pinion set up. As long as that is good then it's fine and no amount of OCIs will affect the wear rate once the diff is broken in. Further, when I had my Dmax, he told me the AAM 11.5 runs fairly cool for a rear diff and that fluid overheating even when towing is essentially an overblown concern. He was clearly right because I added cooling fins to my diff cover and didn't see any appreciable changes in wear. Diff wear is what it is; it won't change a whole lot after break-in.
Wayne you can run this next load WAY further. I would not OCI again until 100k. Just pull the fill plug every 25k and check the fluid level and only top off if needed.
NOTE: for those whom are unaware, Jim Allen is a noted published automotive tech writer. He penned a book about differentials with Randy (of Randy's ring and pinion fame). Jim has forgotten more about diffs than most of us would ever know.