Thanks for the feedback, everyone! Since I cannot patch the game during the game to fix the two glaring platforming issues, I patched it on my domain. It's the game, just now it's playable to the end of the game.
Alternatively, you can go into the dev console (F12 , CTRL+1), go to 'console' and enter something in the command line (until I fix that, here):
pUpgr[5]=1; => Gives you the Escape Scroll, allowing you to leave the mines and return to the world map.
pSelect=0; => In case the pointer for selecting an item disappears.
pY=140; => For the one room where the exit is higher than you jump onto. This will put you in the air, allowing you to move over and reach the exit.