Seeing the points open is wrong, it's soo far off compared to using a timing light.
You do not need a degree wheel the flywheel is 360 mm and 360 degrees .
Timing cannot jump. your points maybe are loose, flywheel loose, switch loose.
You cannot time a puch by ear it's not a small block Chevy.
You got to time about 16-17 degrees before top dead center which is 16-17 mm on the flywheel. You are doing it wrong.
A aluminum cylinder kit will run great at full advance but it gets hot and boom seize it needs a little less then 17 degrees timing.
To find top dead center use a long reach plug or piston stop. Put in the plug hole just enough for the piston to hit when you turn the flywheel. When it hits put a mark on the flywheel and case. Then turn the flywheel the other way until it hits then transfer the mark from the flywheel to the case.
You will have 2 marks on the case and one on the flywheel.
Measure and find the middle of the two case marks and mark it. Erase/ remove the outer marker marks with alcohol. If you put the long plug or stop in just right the marks won't be as far apart so it will be easy to measure.
The flywheel mark when lined up to the middle case mark IS TOP DEAD CENTER.
Now put a mark 17 mm before ( to the left e50, right za50) the middle case mark. When the mark on the flywheel lines up to the 17 mm mark on the case
Under a timing light you are at 17 DEGREES BEFORE TOP DEAD CENTER. No other way is accurate period.
Now you must set points before you run engine to see timing .
E50 spec is 16-18 thousand gap when points are open.
Now here is the flaw with puch point ignition if you gap them at 16-18 thou gap
then even at full retard your at about 20-21 degrees or mm on the flywheel under a timing light which is too high for a kit and you will be taking a chance of boom seizing your engine.
You need to take the stator out and dremel the slots so you can move it more retard or shrink the point gap like 12 thousand which makes you lose kv and dwell.
So in a nut shell stock timing is not good can and will blow aftermarket kits because of heat.
A 40 buck head temp gauge can save you grief cause you can see head temps.
400 degrees is the danger area.
You got issues if your kit don't run and run cool enough with 16-17 degrees timing