I hope you are correct but I have serious doubts.
I don't know anyone who was or is now an FBI agent and therefore have no first hand awareness as to whether they have blind loyalty to the current monster in the White House. However, I have known a Secret Service Agent since we first worked together at another federal agency in the 1970s. Eventually, he transferred to the Secret Service. He has admitted that he and most SS agents are far right-wingers who admire Rethugs for their tough guy attitude. He's a MAGA who loves guns and hates Democrats. If most SS agents feel the same as he does (and maybe they don't) there is no question in my mind that they would likely obey orders from the Leader.
I truly hope that FBI and SS agents, who have different responsibilities, are not in lockstep about unlawfully preying upon American citizens. With 3 and a half more years of Trump and his henchmen we might find out.
As for firings by Trump no one is safe no matter what their job description is. He breaks any law he wants to.