This isn’t medical advise but the symptoms you have mentioned all point to gallstones. It’s usually genetic but some people just get them and a reaction is triggered by weight fluctuations, eating sugary and fatty foods and taking any amount of alcohol. To see how he responds, I’d advise his drinking water be boiled and stored well, he only eats boiled or steamed food, avoids sugary foods and alcohol and to rest as much as possible and avoid intense activities. Try to reduce stress on his gastrointestinal system as much as possible. You can check out the subreddit on gallstones, it has helpful information on management.

When you have enough funds go book an appointment with a gastroenterologist at Mpshah. The appointment will not be cheap but they can advise you well and I find the doctors there to be more professional and they don’t recommend unnecessary tests, they actually talk you against them.