We know that he was aware of the plan to bring Columbina back. How can someone so intelligent and determined to take every possible precaution to ensure his plan succeeds—even putting it above his own ego—allow himself to make such a mistake as letting his enemies prepare and rest for the final battle?

Even if he wanted to give the Traveler time so that, when they tried to defeat him and failed, they would give up and give Dottore what he “needed,” he could still have achieved his goal by making it impossible for them to act at all—such as by killing Sandrone or putting everyone else into a deep sleep.

Unless there is a justification for him making that decision, I consider this a clear plot hole that damages the ending of Nord Krai, since it is not logically possible for the story to be resolved in that way.
Dottore gave the Traveler, as well as the others, days to prepare for the final battle. What justification can there be for Dottore making a decision that so greatly increased the chances of his mission failing?