There is no way Michael would have let Tom go. Tom had too much incriminating info on Michael. If he left Michael, he'd lose the lawyer/client privilege that protected him from having to testify against Michael. Tom would be fair game for law enforcement and prosecutors, who could force him to give info against Michael under threat of prosecution or contempt of court. And, if Tom was nursing a grudge against Michael because of Michael's callousness toward him, he might agree to testify as a kind of revenge. He might be signing his own death warrant, but he might take the chance in order to get back at Michael.