I'd just get rid of it. I have a 2017 Impreza, low oil light came on three times in first 9
months of ownership, dealership did an oil consumption test (failed), replaced part, told me
they weren't sure that solved it, sent me out on another test (failed), replaced short block
(also in November 2018, similar to yours). Car ran fine for about six months, then started
loosing power/stumbling between 2000 rpm-3000 rpm and the oil light came back on.
Dealer did another oil consumption test (passed), i'm still having acceleration issues, and
the dealer is now sending me letters saying they're in desperate need of used Imprezas. I
was planning on selling it to them this weekend and taking over a family member's 2009
Subaru Forester, but that car is currently being towed to a mechanic so.......yeah. From
what I understand oil consumption has been an issue for years with this engine so I'd just
walk away and get something else.