If you have your phone in your pocket while using headphones, can't you just pull the phone out and angle it upwards by about 30 degrees to read the screen correctly? All you have to do is put the phone in your pocket so that the screen is facing outwards.

You can always use speaker phone while your phone is charging. If speakerphone isn't an option, I don't see any problem using the phone while it's charging... I do it all the time and my cable doesn't feel like it's breaking.