I think you found enough wrong in the timing department to cause breathing/tune problems.

Compression does not seem that bad or low.

I agree with the other poster on oil sealing, as it just points and is not definitive.

You could have some excessive carbon but you said the plugs were decent. Losing that much valve lash clearance might suggest a valve seat "has sunk" into its head cavity (counterbore) farther or become much softer.

A previous owner might have stretched a valve while being chased by paparazzi! (:-) A few Volvo's have been owned by a rare few of those who-who's, you know! Like Paul Newman. (:-)

On compression, I think you are allowed a ten percent variance between them all or (if) averaged out and compared to a "rule of thumb" specification from some "usual and customary" experiences for its mileage to power output.

I know 90 to 110psi is shot! 150 to 210 has too much spread between but that's on a properly timed engine too. More evenly across them you need, about, or from a 150 psi and up.
Low to high compression engines vary a lot in their specifications so look up the compression ratio on this ratio engine and see what's is a normal pressure value for it, I guess?

(:-)
Phil