Not going to be remedied by fiddling with timing, PVs, etc. Start taking it apart and looking. Pull the valve covers and bar it over. Look for something not right. Pull the plugs, spin it with the starter and listen. Pull the front and check cam timing, fasteners, etc. Been there. Sucks. Just have to start looking. First vid sounds like it has a miss to me along with the noise.

ETA...A mechanic's stethoscope could be very useful. I would limit the run time until I knew what it was.