I would be leaning towards fuel mixture (wet
plug) and – or timing, not enough advance.
Looking through your pictures I don’t see where
you had the pistons out so stuck rings could
be the issue if you haven’t checked them
through the ports..
If you have a compass pass it across the magnet.
If the compass changes from North to South you
have two magnets. If North points to one side
and South to the other its just one magnet.
Focusing on the magnet is like driving down
the wrong road. You’ll never get where you’re
trying to go.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.