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.