Food is any substance consumed to provide nutritional support for an organism. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals.
If the food has animal ingredients, you must be sure that it is Halal before consuming it. Animal ingredients are not allowed for eating before being sure that it is Halal.
If the food has no animal ingredients, nor alcohol, and you don't know that it has Najis ingredients, then it will be allowed for you to consume it.
It is allowed and not Haraam, but just Makrouh (disliked) to eat in the bathroom. If there is a condition forcing you to eat in the bathroom, you are allowed to do so.
Non Muslim seller who claims that the meat he is selling or wants to sell is Halal can not be taken as an authentic evidence that the meat is really Halal. If Muslim tells you that his meat is Halal and you have no reason to doubt his statement, then you can take the neat as Halal.
Restaurants selling alcohol or pork can never be trusted as utensils and plates used in cooking or serving alcohol or pork become Najis and and every other food put in Najis utensils and plates becomes Najis as well.
Usually we deal with questions related to practical issues which people experience in their day to day life. Your question looks like very far from day to day life, nevertheless if you want the answer for knowledge, it is obligatory to save our life. Deliberate failure in saving life and causing death is a sinful act. It is not permissible to cause death to yourself even if the only food available to remain alive is pork, but no more than what make you survive.
We are been advised to eat less and leave the food when you are still feel wanting to eat more. That will then leave space for drinks and breathing. It comes from your personal experience which makes you able to estimate the one third for food and the other third for drinks and the last third for breathing properly with out feeling full or heavy.
If the meat was slaughtered in any Muslim country by Muslims, we can take it as Halal. Many multinational food companies bring meat from non Muslim countries to sell it in their branches in Muslim countries. Such meat brought from non Muslim countries is not Halal unless there is an evidence that it was slaughtered by Muslim according to Islamic rules.
There is no religious or ethical responsibility for things we cannot control. So, if you cannot control your actions, there is no sin.
However, if you refuse to eat and it harms you or leads to death, and if you can control this and have a free choice, then it is a sin, because it is a sin to harm yourself.
Whether or not you can control this is something you can decide; there is no benefit in being guilty over something which you cannot control, because it will probably just make things worse and add anxiety.
Inshallah I hope you will find a solution that will help you to be free from this problem.
It is a sin to waste food but it is not s sin to give it to others to utilize it when you don't want to eat it for any reason.
Your mental condition needs proper treatment to be a normal person with out anorexia or any other abnormality.
If you were sure that the real Fajr has happened then you ate even after one second after Fajr, your fast will be invalid. If you ate because you were not sure whether Fajr has happened or not and you ate thinking it did not happene yet, then your fast is valid.
The company must not sell pork nor alcohol. Cigarettes business is unlawful according to many scholars. You need to refer to your own Marje' of Taqleed in the matter of cigarettes and seek his verdict in it. Accordingly you will know whether it is permissible or not to invest in such company.
It is not necessary to take it as Najis unless you are sure that food was touched with wetness by a Najis hands. Food cooked with out been touched or by wearing gloves is not Najis.
This is a thoughtful question that shows reflection on the historical account.
Insofar as there is no answer mentioned in history books, it is not possible to give an answer.
If I were to guess, perhaps it would have aroused too much suspicion to bring water, or perhaps it was an emotional and sudden moment and he was not thinking about things, or perhaps some other reason.
Ayatollah Motahhari was of the view that it is not correct that they were without water for 3 days and nights. See https://www.al-islam.org/al-tawhid/vol13-no3/ashura-misrepresentations-d...
I don't think there is historical evidence that they were without food, however, the lack of water is much more dire.
God knows best!