I agree stop worries about it. Your tractor is fine. The rings are fine and in serviceable condition for a 35 year old tractor.
There is some slight wetness but most of that is normal diesel soot for a tractor it's age.
Think about all the old ford's or JD's you see out in the fields still disking or bushhogging, hauling just blowing a constant grey blue cloud. Those tractors probably have 10,000 hours on them and are 30 to 40 years old, the ones km talking about. Rings are worn, there is blowby but until that tractor no longer has the power to pull or uses so much oil it makes no sense to keep it full it's working. When that time comes it's rebuilt.....your no where near the point for new liners!!