Factors that break wudhu

Q: In the English Behishti Zewar, it is written that "Similarly, if there is pain in the eyes and they are sore, and in addition to this they water or tears come out, then too wudhu will break (as in the case of pink eyes). But if there is no pain in the eyes nor are they sore, then wudhu will not break by the mere flowing of tears." Does this mean that the wudhu breaks when we slice onions?

Q: If the blood does not flow beyond the wound but if I touch the blood with my finger and the blood is on my finger. Does my wudhu break?

Q: When I pee, after I rub or press my penis on to the toilet seat there is a light and/or heavy (sometimes) string of fluid I believe, does this break wudhu? Plus how to prevent it? What is it?

Q: Does the wudhu of a diabetic break if he/she swabs the injection site (e.g abdomen, side of upper arm, front of thigh) with an alcohol pad and await awhile for it to dry prior to injecting himself/herself with insulin?