Seriously? Part of the exercise of flying indoors is exactly for that. If the stick response isn't smooth then no amount of training is going to fix that.
Untrue.
Not that any of your difficulties are trivial. It is simply the case that practice (training) WILL improve your control in any environment. Period. You're just not willing to make the investment of time for the return you're going to get.
If you wanted to, you could train yourself to fly indoors in Sport mode, with tiny stick movements. It's not about the drone, it's about the pilot.
My
MM2 doesn't misbehave on takeoff like yours does. It goes straight up. But then, I don't have any extra stuff on it.
As an engineer, I can't support you're trouble-shooting methodology. It's more theory than experiment, which is bass-ackwards. For example, when suggested you swap the rear props to see if there was a problem, you refused on the basis of them being new, barely used, visually inspected, etc.
Okay. That's good enough for you, carry on. Changing them out would have been my first step. I'm a pretty smart guy, but real experience is, well, ALWAYS smarter.