I am pretty sure that from the symptoms you've described, indeed you are suffering from low stomach acid.
stomach acid is supposed to be strong pH 1.5-2 and on demand, which is to say right after we ate.
in your case stomach acid production is weak due to the lack of alkaline minerals in your stomach lining, otherwise it would burn a hole in it.
for the same reason your body is making weaker stomach acid all through out the day so it would be sufficient for at least some kind of digestion. when that acid accumulates especially during night and you are horizontal ( 3AM ) you fill it in your throat.
you need to learn to eat alkalizing foods so your body can built strong stomach lining able to hold strong stomach acid.
also I would suggest you start Moreless protocol which helped a lot of people heal themselves.