How could I output audio to the microphone port on Macbook Pro 15" Late 2011?
Recent Macs (from 2012) have a headphone jack which also has a contact for a microphone, using the same contacts as the iPhone headset. That's how you can record from the headphone jack.

Unfortunately, the microphone jack is not wired to support audio output, so there is no way to do it.

If you want to listen to headphones with your MacBook without a hardware repair, USB Audio devices are cheap and widely available. That would be the best way to go.