Trying to find an effective way of teaching calculus based introductory physics

I have tried a seemingly effective way of teaching calculus based introductory physics. 1. Start class with one or two interesting questions, or a video, or a demonstration, which are closely related to the content of class. 2. Use less PowerPoint but more talking to make the points and keep the lecture going. 3. Reduce the amount of mathematical derivation and only keep the essential derivation; leave the more complicated, time-consuming derivation to the lecture notes/office hours. 4. Lecture less examples to leave around 10 minutes at the end of class for a simple class quiz which will be graded. Several years of practice proves that this method can reduce the number of students who play cellphones, increase the number of attendance, and reduce the number of dropout. The drawback of this pedagogy is that my workload is increased as I need more time to prepare the class and grade the quiz.