Oh I’m definitely no fan of dealers. I’m completely on board with DIY care for your Subaru. But ESP is a top-tier oil, and I think you’re selling yourself short with the ~2.8k OCIs. I’m down with the filter adapter, but I’d run the Fram Endurance 10575 (which is what I run on my EcoBoost). If it were mine (and I respect your choice if you’re not good with this) but finish this OCI wherever you’re at. If it’s still in the same range as all your others, you’re at a point of stasis.
Next OCI, use your ESP stash, grab the Endurance 10575, and go at least 5-6k on your next sample. Iron tracks with mileage, but it’s a known fact that Mobil 1 “appears” to show more iron in UOAs than some oils, but if your trend is all Mobil 1, that’s “your” trend. Your trends are not comparable to others directly, so don’t necessarily bother with B-S’s numbers. A few PPM is not the end of the world… as long as it’s consistent.
In the GDI world, fuel >5% or dropping out of grade are valid condemnation points. That’s what I would use if you like the ESP. I’d personally use Polaris or WearCheck if you’re going to use fuel % as a condemnation, since B-S’s number is an estimate. But to know for sure where the “safe” point is for ESP, your engine, and your driving habits, you’ll need to stretch the OCI until you bang right up against the condemnation points or just over.
Then you can know the mileage point where your oil choice and your engine/driving combo intersect and minimize your cost relative to protection.