You are fine, just change the oil.
My '14OB has a 7,500 interval, in 2015 Subaru reduced the miles per oil change to 6,000 (for the same engine) because some of the FB motor can sip a little oil and it was freaking folks out who saw the low-oil light. This motor does NOT have direct injection so I am less worried about fuel dilution. Because Subaru requires Syn, going to 10K will likely be perfectly fine.
Don't add additives, don't add 0w40, don't do anything other than new oil/filter. A UOA might allow you to sleep better but likely the oil will "fine" with active TBN from thee result.