Yes, you want to find a speaker with a flat sound signature.

This is a type of speaker called "studio monitor".

Remember that sound is very unforgiving when working with it, every single step in the chain of recording a sound to playing it back can change how it sounds, with the changes to the sound being compounded when you play it back.

This includes the microphone, the microphone amplifier, the speaker amplifier and the speaker.

This does not mean that it is impossible to do what you want, but be prepared that the sound may sound strange from what a normal stethoscope would produce.

I'm afraid I can't answer your technical questions, I'm really not that knowledgeable about this. All I know is you ideally want the frequency curve to be flat, I don't think it matters much where it sits relative to that line.

Honestly, that Danon dropping off at the low end is pretty typical though it's one of the better ones. You'd really just have to test it I'm afraid, it might be totally fine to chop off the bottom for some things but maybe it's necessary for certain heart conditions, I wouldn't know. If it were an option I'd say the best bet is to always stick to the analogue, but I'm absolutely with you on hating traditional stethoscopes, they're so painful...

You probably can just leave the crushers on your neck with the volume maxed out, but I'm really not sure if that'll work. In all honesty the speaker might be worse due to the way the acoustics in the room can change what you hear, it's really hard to say.