People here have made a strong case for Michael whacking Fredo, even if he came clean, because his betrayal had nearly cost Michael and Kay their lives, and Fredo couldn't be trusted. I'm not saying they're wrong. But I feel even cold-hearted Michael might have given Fredo a pass if not for that outburst. And, if he volunteered to tell Michael about Frankie and Questadt before Michael's testimony, it'd work in Fredo's favor. I think he'd probably banish Fredo and be wary of him forever, but I don't think he would have had him whacked.
As for the Senate hearing:
When gangsters are called before Congressional subcommittees, they always "take the Fifth." They're not interested in convincing people that they're legitimate--they just want to avoid prosecution. But Michael insisted he was completely legitimate. Imagine, when the Senator asked him if he was responsible for planning the massacre of the heads of the Five Families, Mihael gave the Fifth Amendment answer, "I refuse to answer that question on the grounds that my answer might tend to incriminate me." Everyone would have known that the reason his answer might tend to incriminate him was that, yes, he did plan it. That would have been the end of his "legitimate" persona and it could even have cost him his casino licenses and invited more investigation.
I think if he knew in advance about Frankie and Questadt, he would have reached for Vincenzo and had Tom arrange--demand--that Frankie's brother be allowed to visit him at the Air Force base. That in itself would have let the Senate subcommittee know that Michael knew they had Frankie. They might have refused to let Vincenzo visit Frankie. But then Tom could have had news reporters on the family payroll blast stories about Frankie's survival, how he was an arch-fiend set up to spill lies to save his own hide, etc.--possibly enough to invalidate Frankie's credibility even before he testified, maybe even enough for Questadt to withdraw him as a witness. But even if Frankie did get sworn in, Michael would have produced Vincenzo at the hearing. I just can't see Michael taking the Fifth.
