No sure what you mean by sexual (do you mean a real sex scene, or just reference?)
Annotation--Warbreaker Chapter 6 https://www.brandonsanderson.com/annotation-warbreaker-chapter-six/
Yeah, Vivenna was my least favorite POV character, too.(try not to skip too much from chapter 35 might be a good idea, she is kinda important)
That really depends on your definition of things speeding up, but for me things got better from chapter 35 or so.