That was a long read and I’m still not sure what you can and cannot eat. Maybe you can make a good/bad list.
Restaurants don’t do well with special requests. Lots of dishes have a sauce with some type of sugar. Avoid dishes that require rice. One trick I learned in Taiwan is look at everyone’s plate for ideas. Use Google maps photos for ideas. There are a lot of buffet and pay-by-weight places once you recognize them cheap and easy to point at what you want.
Fried rice is made with soy sauce.
Grilled meat comes without sauce but most meat dishes have some sauce included in the dish.
Maybe consider a modified Keto diet. Avoids sugars like rice, bread, sauces… It helps me avoid all those. Ketogenic "Keto" diet in Taiwan