Lastly, you ask, "was Capone aware of the plot to kill Masseria? And later Maranzano?"

None of us were in there room when it was discussed, but my guy tells me no! For the simple reason that he wasn't involved because he wasn't needed to accomplish either one of those killings. And I would imagine that the perpetrators, Lucky Luciano and his confederates, would be sharp enough to play such deadly chess moves as quietly and surreptitiously as possible, no?? That only makes sense.

Capone makes what is a good move joining Masseria and then his benefactor gets killed? And probably nobody clued him in on it
Does Capone immediately start looking over his shoulder ?
Does he believe Luciano or the others now at least temporarily on the clannish Maranzano Castellamare side, when tyhey tell him he's saf.That the remaining Chicago Maranzano/Aiello bunch won't take him out next ?