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.
This goes to the initial premise of my initial comment. He either has blanket immunity for anything involving Covid and his handling of it - which is what the pardon has been characterized as, or he doesn't.
If he claims he doesn't (which would then allow him to be prosecuted for Covid-related crimes) then can take the 5th. If he claims he does have a blanket pardon, then he cannot invoke the 5th legally. IMHO it's either or.
I think Senator Rand should just flat out ask him under oath: "Did you accept the pardon that was offered to you by the Biden administration?" If he answers yes, then he's immune and can't plead the 5th. If he says no, then he is open for criminal prosecution for his actions during the Covid pandemic.