Regarding your oil change interval, your ‘15 model is identical to my ‘16, and per the guidelines in the Diesel engine supplement I’d say your mileage is about right. The Ford and GM diesels use a different means of DPF regeneration, and that does have a significant effect on oil life.

Also, you should be following the “Severe Service” oil recommendations. Hauling your TC probably has your GVW maxed out, and the terrain you’re traveling, ambient temps, and bio-diesel usage all have an effect on oil life, and the type of oil you should be using. The recommended oil for severe service is 5W-40 CJ-4, which is only available as full synthetic. It even says this on the oil filler cap.

I only mention this because when I was taking my truck to the dealership to take advantage of the “free” oil changes they offered when I bought my truck, they always wanted to put 10W-30 non-synthetic oil in it. After the second time of arguing with them, and making them drain out the non-synthetic, I went back to changing my own oil. Free isn’t free if they’re doing it wrong.
Also, this was the first vehicle I’ve owned that had an oil-life minder to tell you when to change the oil, and I was curious as to how accurate it was. My concern was that it was telling me to change the oil too late, rather than too soon, so I sent a sample in the last time I changed the oil. I’m not interested in getting every last mile out of the oil.
Like yours, my oil minder had gone from “change oil soon” to “change oil now”, and I had driven a couple hundred miles beyond that. The report came back saying it was still useable, and the only concern was that there were some oil additive components present that should not have been in the “synthetic” oil I had identified on the submission form. Those components were apparently from the ~1 qt. of non-synthetic oil that was left in the filter from the last “free” oil change.
So like I said, I change my own oil now, and I trust the oil life minder.
:):)