Regarding the fact that going down the ladders sometimes it happens that the bag falls by itself, I think it's a problem with your controller. It has never happened to me, neither using the keyboard nor using 2 different controllers. Just as it never happened to those who tested the game for me.
Regarding being able to move the controller diagonally to go up the ladders and then turn left, I don't know that the original arcade version has this. From some searches on the internet, I always read that the joystick has 4 directions, not 8. And anyway, emulating the game on MAME and trying to move the joystick diagonally, the character freezes completely. Perhaps you have found a version of the game that allows you to use the joystick diagonally? Or does MAME have an option that allows this?
Regarding the fact that when you drop a pickaxe the 4 seconds timer doesn't reset, it's actually not a bug in the game but a wrong transcription in the instructions. The 4 second reset timer is only for Bagman Strikes Back. In copying the instructions I forgot to delete that part.
Regarding the AI of the guards, I honestly never understood how the original version works. I tried it on MAME, but if I position the character on a ladder and move continuously up and down (making noise), even if the guards are nearby, it is not certain that they move towards me, on the contrary they often drift away. Anyway, I didn't want to create an identical port to the original, but to create a game based on it but with different features, such as more completely different levels. I also personally feel that the arcade version is too difficult for most people, so I wanted to make the game a little easier for as many players as possible to enjoy it. The fact that you are a super champion and can complete the level dozens of times does not mean that it is easy for everyone.
In any case, as far as I'm concerned the game is long over and what you see is the final result. I'm only willing to get involved in case of bug fixes.