Howdy,
With the simple paper test for vacuum over the oil fill shows what? blowing or vacuum?
OK, you have break-in oil in the unit. You have monitored the oil level at all times? is it using oil?
What does the exhaust smell like? say at 60% power, say at your 80-81% problems, what does the exhaust smell like?
You said he honed the cylinders. Maybe the cross hatching is not present, and ring pressures are glazing the cylinders. The first video looks like your unit is running on oil. As in its running on diesel fuel, and at the 80-81%, the system oil is blowing past the rings and firing in the cylinders.
Earlier you stated you had to add more oil.
Cylinder compression could be a issue. Hydraulic lock? the bleed down for proper installation for valves and lifters. Maybe a valve is bent, valve lash is out, but, you never said if you have vacuum or blowing from main crankcase.