Did you check for blowby at idle? I.e., take the oil filler cap off while running, rest it on the opening and see if it dances. If it sits perfectly still, I wouldn't even begin worrying about blowby. The breather hose I would think it more likely due to wear on the hose. If it's leaking around the valve cover, it could be a worn valve cover gasket or maybe an improperly torqued down valve cover.

If it's coming from around the intake, that might be due to a tired intake gasket and a lot of gunk in your intake due to EGR. Unplug EGR, clean intake out, replace gaskets.

But as far as blowby, I'd start with the basic blowby test. And, like Tyler said, even if you have some blowby, not much you can do about it ... just drive it and enjoy it as long as it starts/runs OK. Lots of high-mileage MBs have some blowby (and some have a lot!).

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)