If a man kisses his wife whilst he is fasting and emits maniy, then he has invalidated his fast and he has to make up that day’s fast after Ramadan ends.

Your fast is not invalidated because of the effects of sinusitis, such as mucus, blood and the like. But if you are able to expel it and spit it out, that is preferable.

If the emission of semen happened because of a wet dream while fasting, then this does not invalidate the fast. If the emission of semen occurred as a result of masturbation, then your fast is invalidated.

If a person intends to break the fast whilst he is fasting, his fast is invalidated if he decided to do so and there was no hesitation. If he changed his intention after that, then he has broken the fast and he has to make up that day. If a person wavers in his intention of fasting, his fast remains valid because the basic principle is that the fast remains valid.

The view favored by Ibn Taymiyyah is that putting eye drops while fasting does not break your fast.