To invoke the 5th amendment there must be a reasonable risk of prosecution. For example:
Mason v. United States, 244 U.S. 362 (1917), is a U.S. Supreme Court decision holding that a witness invoking the Fifth Amendment privilege against self-incrimination must show a reasonable, real danger of criminal liability rather than a mere speculative possibility.
From Justia: Prosecution may be precluded by tender of immunity, or by pardon, Brown v. Walker, 161 U.S. 591, 598–99 (1896).
Yeah - this is among other things a perjury trap. Sorry - self-incrimination is ABSOLUTELY on the table if Fauci doesn’t take the 5th. It’s just true.
That also isn’t the source you used before which at this point I have to believe was self-written opinion. That’s fine, but your own actually authoritative source says right there that if there is a reasonable danger of criminal liability (perjury if he testifies TODAY post-pardon in any way that either disagrees with his previous testimony or his diary entries). Since his diary entries clearly conflict with his previous testimony, there is no way he can answer questions and not commit perjury.