By the way, on all that Flynn stuff with Judge Sullivan thinking of bringing contempt charges ... I don't think Sullivan thought the contempt charges through. I think any contempt arising from "perjury" involving the guilty plea would have to fall under indirect criminal contempt. Direct contempt is meant to be an immediate punishment for actions that are making it impossible for the court to function (e.g., when the defendant spits in the prosecutor's face or starts screaming at the judge). Although Sullivan is apparently thinking of holding Flynn in contempt for making false statements at his plea--which would have been "in the presence of the court"--Sullivan did nothing at the time about it. So, in order to hold him in criminal contempt at this late remove, it would have to be indirect criminal contempt.
And indirect criminal contempt is a new criminal charge, which means Flynn would have a right to counsel, discovery, a trial, a right to confront witnesses, etc. Sullivan would actually be creating a huge problem because he would, in effect, be asking the government to prove Flynn knew he didn't make material false statements to the FBI but decided to plead guilty anyway. And so Flynn would certainly have the right to explain that he felt forced to plead guilty because of the threat to indict his son. (This is very different from the ordinary indirect criminal contempt charge, which revolves around rather simple, ancillary matters, such as, e.g., whether the defendant violated the court's order by having contact with the victim or complaining witness.)
Besides, for a statement to be perjury, I am 99% sure the defendant has to make a false statement of fact, not a false legal conclusion--and materiality is a legal conclusion. I'm sure Flynn admitted to making conflicting statements to federal investigators, but it's not perjury for him to believe at the time of the plea that his statements were material.