You have a number of facts wrong.
I’m not sure what you mean by “whistleblower rules” but the statute has not changed recently and there was never any requirement that the whistleblower say how he knows. The practicalities are that the more the whistleblower says, the more likely the result is a thorough investigation, but there is no requirement of first hand or third hand or any hand knowledge. A wild guess will do if it’s correct but a wild guess is unlikely to get a look. Don’t forget (if you knew) that the inspector general has to certify that the complaint meets certain standards or it never gets to Congress.

You are mistaken about how warrants work. The warrant itself may be destroyed by somebody pissed off at being served, but I sign three copies. One is presented to the target, one is for the police, and one is for me. The return always comes back to me stating when and where the warrant was served and by whom and with an inventory attached of everything that was seized if anything was.

In a FISA warrant, there is no seizure and you are right that privacy is lost but I think the theory is that since the whole process is secret, you are not harmed. I was opposed to the creation of the FISA court and have not changed my mind.