I think get the sump off and cleaned out, try to get engine flushed out aswell and defo a new oil modine, and then you will have a starting point, if your confident that your sump is clean, and have a new modine, well then if you get more fillings, then it like bearings, but metal should have a copper colour off it.
As Duffman said, i wouldnt do a rebuild untill i had to... and in that event be vewry carefull who you get to rebuild, Subaru engines are a bit more tricky than others, so someone with Subaru experience is essential