Not exactly.
While I think the Whittaker "acting" appointment is perfectly legal and in order, senior positions that require Senate confirmation do not really conform to "the boss makes the choice".
Andrew Johnson was impeached and almost convicted over an issue like this (he fired a Senate-confirmed cabinet member over the objections of the Senate), so it will be interesting to see how this plays out.
If a majority on the Court want Trump removed, it is possible that they will hear this case and rule for Rosenstein.
I am as pro-Trump as anyone here, as you can see from my posting history. But there are lots of serious people, swamp-dwellers for sure, but serious, who would be happy to see him go as long as their fingerprints were not on the murder weapon.
But would Article II of the Constitution “trump” the Fed Vac Act? Both are Federal laws but is either higher then the other?