The policy of eNotes is to answer only one question per posting. I suggest you submit additional questions about each of the acts. There are many ambiguities and unanswered questions in the four acts, and there are many possible answers.
Please refer to the discussion of one unanswered question by clicking on the reference link below. The question is: "Why didn't Macbeth kill Malcolm and Donalbain at the same time he killed their father King Duncan?" Many answers have been offered in this discussion.
Since Malcolm had been named Duncan's heir, and was the obvious heir as his eldest son, it would seem that Macbeth would not accomplish his objective by killing the King and not killing Malcolm. Macbeth had no way of knowing that Malcolm and his brother Donalbain would flee immediately, thus allowing him to blame the King's murder on them. One answer seems to be that Macbeth was so unnerved by killing the King that he couldn't force himself to commit any more murders that same night. Furthermore, as he tells his wife:
Methought I heard a voice cry "Sleep no more!
Macbeth does murder sleep"
Still it cried "Sleep no more!" to all the house. (2.2.)
This suggests that he was afraid this voice would wake people up and he would be caught red-handed with the two daggers he had used for killing Duncan; so he had to give up any thought of killing Malcolm and Donalbain, if that was what he had in mind.