I finally noticed that you attached screen shots and looked at them.
You actually have the opposite problem from most Bluetooth users: MC complains to you that it can not play 48kHz through "core audio". In the normal scenario *ONLY* 48kHz can be played, but almost all music is sampled at 44.1kHz. So the message says that it can't play 44.1.
So why can't yours play 48? Hmmm... Well, first of all, you are using the default audio device and that device follows whatever you have selected in "sound" on the mac's sound control panel. I would start by changing the audio device in MC to be the *specific* bluetooth audio device that the Mac sees.
Tools > Options > Audio > Audio Device > (find and choose your device)
Then restart MC, and try to play something.
If this doesn't work, you might include any screenshots that might give additional clues or information.
Good luck!
Brian.