Kamen you will get varying advice because perception is reality and we tend to have different experiences with these cars.
I've myself kept reading about blown this and that, you read enough and the whole car is a ticking time bomb, you should simply walk away from Subarus period.
I am not dismissing the cautious advise you were given, it is sound.
But my opinion is a long OCI will not necessarily lead to a dead turbo/engine.
It also depends what oil was used, how the car was treated, if the oil ever ran low.
These are the unknowns. An OCI is not an end all be all because from what I was told it only measures particulates in a certain range and can very well be blind to others.
If I were the average person I wouldn't be comfortable with you doing any extensive testing either. You want the car or not?
To me it sounds
like you've been dilligent when looking at this car. Only you will have that feel if you should or not pull the trigger.
It's not the only OB out there, maybe you should keep looking?
I won't have ANY record of my maintenance when I sell this car other than my own notes in Google Calendar.
I do all my maintenance myself.
If this car wasn't used in city traffic and the lapses are not extensive in months AND the owner can account for said lapses, sounds to me like it should be OK.
I wouldn't want to buy it maybe because of the other things you listed. Windshield cracked, some damage to paint, etc.