Tetzaveh - The Holy Ripple Effect

Why did Hashem instruct Moshe to appoint Aharon as Kohen Gadol, instead of Hashem speaking directly to Aharon? What was the advantage of Moshe in his role of bringing the Torah to Am Yisrael, as opposed to Aharon as Kohen Gadol? What is behind the teaching of successive 'whittling down' from the whole world, to Israel, to the Beis Hamikdash, to the Holy of Holies? How does this parallel the 'whittling down' from all the nations, to Israel, to the Levi'im, to Aharon? Why are the Levi'im counted from the age of one month, whereas everyone else is counted only from the age of 20? How does this parallel Yocheved, daughter of Levi, who was counted as part of the 70 who came down to Egypt while she was in utero? How do these concentric circles form and connect to Hashem, sending light out from the center in a Holy Ripple Effect?