Gas pedal stopped working, battery died

Yesterday I forgot to replace the cap after adding oil into my engine. Drove
about five miles that way before the cap was replaced. There was oil all
over the engine, my dad applied engine degreaser and then I had to spray
it clean at the car wash. On the way home, the brake and battery light
came on. A couple miles later, the gas pedal stopped working entirely. No
acceleration or revving. I had to roll my window down just to be sure the
engine was on. I drove the rest of the way home without use of the gas
pedal. I parked the car in the parking lot. 20 mins or so later I came back
out and started the car. Based on the way it sounded when it cranked, the
battery was low. But it did start up. While parked, the gas pedal seemed to
be functioning just fine. I did not attempt to drive anywhere or take it out of
park. However I left the car on to idle until the battery was basically drained
(lights started flickering and radio light went off) which took maybe 20 mins
so I'm assuming the alternator is no good. The alternator was replaced last
year. Did the water damage something? What caused the issue with the
gas pedal? Check engine light has been on since I bought the car over a
year ago (for an evap leak) so Im not sure at the moment if any new codes
have popped up.