The correct answer is "His efforts to soothe himself render him earnest and genuine".
In this excerpt, Oskar's credibility isn't really affected in any negative way. Yes, he's suffring from sleep deprivation, but the tone of his speech is remarkably calm. He's suffering yet he's emphasizing all the things that make him feel comfortable. Oskar's ability to be vulnerable and take the focus away from his struggle and into positive things, paints him in a very good light.
Hope this helps!