I'll tell you one thing that will help salvage his reputation.
Explain, in public, precisely what conversations really took place between himself and O'Callaghan at the time. Why did he recieve so much more than Morter for example? It cannot be explained by their relative volumes of work. It is curious that he tip toes around this to the extent that he does, when a simple, frank admission of the discussions, even if he knew at the time, or has now figured out that he disproportionaly benefited, would clearly show him in a more sympathetic light. Passing on money to others, which he describes as a huge mistake (it was) actually isn't what the public would naturally have a problem with. It is the extent to which he personally benefited measured in pounds, shillings and pence. Putting this in the context of his up to that point constrained personal finances, having a large family, the cost of living etc and just being a bit contrite about that, but on the insistence that there wasn't anything illegal about that, but not doing a mea culpa about the things which people don't really care about that much, I think would really allow him to reset.
But there is something holding him back from doing so. If it is loyalty, it is misplaced.