I don't really understand the bit I have bolded above. How do you espouse a theory and impugn others without defaming them? You are incandescent with rage that the Met have espoused a theory and impugned others in the Ben Needham case for example. What's the difference?
Your thinking, like mine, is shaped by the anglicised interpretation of what amounts to libel.
I think the Portuguese one is very different.
I also think Amaral is handed much more licence than he would otherwise have because he quit the PJ before his book was published, rendering him free of liability for breach of judicial secrecy in getting his book onto the shelves so soon after the archiving, and entering into the public domain an account (of an event) that competes with Kate's account.
Under those conditions, by Portuguese law, you can say (almost) what you want, with scant regard to such considerations as truth or accuracy, and get away with it.