Questionengine lackes power. compression=120psi.looks like blow by near block-head junction.(oil spatter) could be missing a head bolt in this area. there is a hole in shroud where a bolt could have been,but there seems to be a bolt underneath. hard to see with shroud in place.
Answersounds like someone had apart, didn't do job correct.
you need to replace that bolt in head. i would remove them all, check head gasket, match up bolt missing and replace head gasket .
also fix that shroud . it could be your crankcase breather should be cleaned out wash it out with a cleaner fluid.