the .020 point gap is just a reference static timing is the correct method also point push rod length does not mean anything ( does not matter if the push rod is worn .050 it will only push what the camshaft lobe height is ground at)
Normally what happens is the camshaft wears and this shortens the stoke for the point rod so you end up with a smaller point gap like .018 .
sounds to me that the engine has been apart before or assembled at the factory with the timing marks off one tooth or ether the crankshaft or camshaft were incorrectly orientated when they were machined originally
With that being said how you are getting a larger point gap is because you are starting farther down on the shallow side of the camshaft points lobe when you static time if the timing marks are off . this increases the length of stroke for the points push rod. increasing the point gap