Rgr, You only found the front diff bolt was loose and aft ones were tight. I was hoping the diff had slid aft. But that really not the issue as the rub area you circled is above the CV adapter not just aft.
The CV adapter is bolted directly to the output flange of the diff so there is no movement of that part during operation. Ed's advice to remove the spring from the perch and run the suspension thru its travel limits would be useful IF the issue was outboard of the CV.
I assume you've pushed and pulled on the CV adapter to see the possible the internal bolts were loose?
Its not at all unusual for the BDR axle bolts to loosen. I've come very close to launching an axle (two bolts remaining). Why I drill my bolts and safety them, Locktite 272 and Locktite primer were not enough to prevent the issue.
Back to my earlier post on the possibility you flipped some the trash in there. The purpose of the paint is to see if you have a new rub of not.