What explanation did Tanis offer as proof that he had not betrayed the group?

Tanis offered several concrete pieces of evidence supporting his lack of betrayal, including that of Kitiara's state of shock upon realizing that both her brothers were on board the Perechon. She hadn't known, so therefore Tanis couldn't have betrayed them. He also explains that had he simply given up the Green Gemstone Man, and Tanis would have the rulership of Krynn given to him from the Queen of Darkness herself.