By-the-by: It's not just the 19J that suffers cracked pistons. An unlucky mate of mine had two 12J's in a row let go. The one in the vehicle originally had three pistons cracked; the "it's a low mileage minter, honest mate" replacement he obtained had suffered the same demise with all four. I suspect in the first instance it was timing or injector related as he could never get it to run right. The second one is anybody's guess.
If you're reading inconsistent compression between cylinders, it's time to take the head off regardless. Whatever you might need to do to rectify it will require access to valves, pistons or the gasket itself, so grab a decent gasket kit, get spannering and hope for the best would be my approach here. From the video, my money would be on cracked piston, broken rings or a serious gasket failure cylinder to an oil passage.