When I plug in my headphones the audio is choppy and distorted.

The phone's display is stuck on and wont change screens, even pressing the lock button has no response.

There are several possible issues. Try using a different power adapter first to see if this solves the problem. If not it could be an issue with your battery or charging port on the phone. Check to see if the connection is loose where the adapter plugs in, as well as if the battery is properly connected to the charging terminals in the phone. For more information reference this troubleshooting guide. Hope this helps.

Try turning off the phone by holding down the power button for an extended period of time. If this doesn't work also try plugging the phone in as well as removing the battery pack to force a restart. For more information reference this troubleshooting guide.