Do yourself a big favor and get another professional opinion from a tech who knows your car, like a Volvo master tech. That engine shouldn't be THAT bad at that mileage UNLESS it's been abused, neglected and/or driven overheated for a long time.
Normally, those engines should go well over 200K miles w/o major problems. If someone who said it has too much blowby said "might be a clogged flame trap" (non-turbos only) then why didn't they just fix it?
The "piston pressure" was determined by....? (compression test, specs?) or cylinder leak down test? (best way to determine actual area of compression loss if so).