Hello Siebe,
you said: “A lot of medical treatment, for example, comes with sufferings. The doctor or parents who know the treatment will come with pain and trouble do not act immoral.”
Sure this is not immoral. Moha can be translated as “morally blind” or “ignorant of the true nature of this world”. The medical treatment causes pain but is done with the intention to heal and to help, which is a moral act. It is not done with the intention to harm and to cause pain (that would be moha).
Your other two examples also have the goal to gain a healthy status of the person. That is always a good or kusala intention.
Kamma is intention. If intention is kusala, kamma is kusala. The possible pain associated with an action is embedded in the nature of this world. In your examples pain is not the intention. Thus the medication is given with sorrow for the pain caused but with good intention and the knowledge that the gained health is much more worth than the short lived pain.
Tobias