Are you sure that it is coolant? It maybe condensation and that's normal.
worn out muffler bearing
YES
depends on what year. If they are new then yes they would
Not likely. But you know you have a hole in your muffler so unless you want to have an accident from carbon monoxide poisoning you should have it replaced ASAP. Then reset the light and if it does not come back on, you know that was the cause.
If you were to cut off your exhaust pipe the muffler would come off with it, sence it is attached to the very end... I would be alot louder, it might hurt your MPG rating....
Originally it would have come from the factory with GREEN colored antifreeze ( meeting Ford specification ESE-M97B44-A )
a gas line over the muffler may have broke, or you car is older then 20 year old
may be the bird is not hungry
Your bad muffler might be part of the reason your check engine light comes on. Usually, your bad muffler causes something else to go wrong and that causes your check engine light to come on. Problems cascade.
Heater core leaking.
According to the 1997 Ford F-150 owners manual : It would have come with green colored antifreeze from the factory ( meeting Ford specification ESE-M97B44-A )
Something to check would be if there is rust in the break-drums that would need to be cleaned. Another possibility would be the strap around the muffler. Check to make sure it isn't broken. If it is, the muffler may be hitting part of the frame, hence the noise. Other than that, I have no idea.