It's obvious that you put in a lot of hours, as i said very good job you've done.
When i play i can finish level 1 and 2 ( 8 rounds ) with 1 mario :-)
About the extra levels: i finished level 5 and gave up on level 6, in my opinion there is to much "waiting" time in it. For that reason i stopt trying to manage 6, 7 and 8. The style of the levels is okay, it looks nice but i like the old stuf 1,2,3,4 and all over again....
I prefer running with mario quiting the rounds as quick as possible.
The glitch in round 1 (ladders and barrels ) in level 3 was up on the first ladder. At the very very end, on a certain point mario turned the back at you, than you had to jump to the right en mario was gone and the level fnished. He didn't bounce back at the invisible wall. You had to be quick because of the approching barrals. I bet there are no video's of it. Back then we had no smartphones with camera, ( but we where happy hahaha )
Then there was another thing i now remember. We called it holding hands, on top of the ladder. In a certain position barrels did not come of the ladder and gave some relaxing time.
It's a long time ago, i was 11 when donkey came. In 1986 we almost went broke on this game hahaha
Greetz Andreas