If you try hard to get rid of the blood that accompanies the saliva, then whatever is left of slight yellow traces in the saliva does not affect you and your fast is valid.

If the gastroscope is inserted into the stomach without introducing any other substances, then it does not break the fast, but if some greasy substance or anything else is introduced with it then it does invalidate the fast.

X-rays and ultrasounds do not break the fast in and of themselves so long as the patient does not consume any drink or medicine through the mouth or nose.

If the nose drops are small in amount such that they will not reach the throat, then there is nothing wrong with that, but if they do reach the throat and can be tasted, then the fast is invalidated and has to be made up.

If fasting causes you to vomit or become dizzy because of physical weakness, you can break your fast but you have to make up for the missed days later.

Hitting someone and shouting at someone are not things that break the fast even if it is done by way of aggression.