You could have Helicobacter pylori which may be causing your stomach ulcer and gastritis. That could of occurred following achlorhydria/hypochlorhydria giving pylori the chance it needed and the SIBO too.
Destroying Helicobacter pylori might be needed so look for ways of accomplishing that. Judging by your other threads, you have already discovered this.
PepzinGI (Zinc Carnosine) might help you in the short term and so could Lactobacillus Plantarum. As could licorice root as mentioned by another poster in this thread.
If you need Vit C, then get it in bulk powder form rather wasting money on capsules. I just received some (2Kg) today along with a few other things from Trade Ingredients. The prices are very decent and so is the delivery.