There are lots of things that can affect a sensitive digestive system. Even vegetarian food. My mother in law can put a whole garlic bulb in one vegetable dish. That is before she puts in excessive huajiao, lajiao, and other culinary chemicals.
Fried rice can be a major cause of food poisoning, if the boiled rice has been left hanging around a warm kitchen all day before frying. Tofu can also go sour in the same conditions, and has perhaps caused me the most cases of laduzi. Perhaps two foods to be avoided if you are sensitive.

As a general recommendation, I avoid large hotels and large restaurants, as they have a large menu to keep on the go and the food can be poorly kept for longer periods before cooking.
I like a lot of the Muslim places. You know that they will have washed their hands at least 5 times a day. They also have very good beef. More for lunchtimes, but there is a big Muslim eating hall/open area (2nd floor) outside the Youngning Mosque next to JinMaBijiFang. Also there are a lot of restaurants that do the same kind of canteen buffet foods in the area around the Shuncheng Mosque. Some in the walk through covered areas. There are canteen style places that plate the food individually for each person. The advantages with these places are that they are cheap, and you can see what you are going to buy before they plate it for you. Your friends can choose the foods that take their fancy without the mystery of a menu.

If you are near NanYa on Dianchi Lu. On the opposite side of Dianchi Lu from Nanya shopping centre there is a bus stop area, for busses heading south. Directly behind the bus stop, is a Haárbin restaurant. This is northern food, mostly meats, and not spicy. They are quieter in the evening, than lunch times. One of the specials, at the top of the menu is pork back ribs, that have lots of meat on them and are reasonably cheap.

@Janjal, some other consideration.
One aspect of learning, is your fellow students. If most of the students in the class are Asian, they fit in well with the learning style, and you will be the odd one out. If you do a class with mostly Japanese SS they will have no problems with reading and writing and you may get your confidence undermined. By contrast, if most of your fellow SS are western, then although the norm in a university is the Chinese teaching style, you will all be in it together.

A few universities (e.g. Shanghai, Jioatong) separate the students and have a different class methodology for western SS, than they do for SS of other Asian countries.
If your teacher is a fresh graduate of teaching Chinese to foreigners course, they may be a bit rigid in their methodology. A more experienced teacher will know more of the quirks of teaching westerners.

One advantage of learning in a university is the cost is much lower, and there may be cheap accommodation. Also if you are a younger person, it is easier to connect with local students who may even be your dorm mates.

The advantage of learning in a private language school is smaller class size, more flexible teachers, and different methodology and course materials.
The other big difference is course materials. Most university courses have a lot of university vocabulary (admissions, cafeteria, library speak) that you will not use, and this is front loaded on the course and can be frustrating if you want to go out and use the language.

Cheap places to live. Kunming is not cheap, most Chinese tier 1-2 cities are not. As @waynecaoaus noted, most of Zhejiang uses Mandarin (maybe because it is not mother tongue but learned, it is more standard) there will be lots of small cities along the coast dependent on trade that use the language daily for business. These would be cheaper places to live.

As for the other things, maybe it comes down to whether or not your focus is learning the language, or if you are using learning Chinese as a shoe in for visiting China longer term. A lot of students are probably the latter.

@cloudtapezer. Damn, I think you are right. They got me.

Most employers HR departments will be able to provide a letter confirming the period of time you worked there (they will have tax records), even if they cannot give any information of your job title (which most can).
If you write to them and let them know why you are asking, when you worked there, which site/dept., your job description, and if you can remember your line managers. This should help them a lot. Your employee or tax number would also help.
Some companies/institutions do not allow managers to give personal recommendations, but will be able to confirm that you worked there.

Any letters they provide should be on headed notepaper. Scans are usually accepted for these letters, but check with the visa office about that. Rules change.

There are also opposite examples (also happens in the west) of parents keeping the kids out of school, or pulling them out at the earliest legal age, so that they can work in the family business or on the farm.

Much of Yunnan is still an agrarian economy/culture, there are also some minority parents/grandparents who do not want the children losing touch with their minority's culture. They want the children to stay in the village and stay on the land.
There are also those parents/grandparents who had no real education themselves and do not see a need for it, which we may view as ignorant.