If you can't turn on multiple accessories with the engine running, it sounds like your alternator is not putting out enough or any juice. I don't know the exact science, but Ford alternators can fail in a way that will drain the battery. I had this happen a couple of times to me when I owned Fords. I also had one fail in a manner that set my Mustang on fire.
Your battery also completes the circuit so it's possible that it's shorted internally causing your power problems. So, I'd replace battery first. Running a battery down that low several times will kill it in a hurry, plus it's beyond it's useful life.
If you still have power problems with the new battery replace the alternator, too.
