So as a student I'm happy that you're looking for feedback and I've got some for you and hopefully it'll help. My history teacher has a really good method of teaching us about a war. She will break it up into major battles and ask us for homework to make a quiz of the war using a certain number of question from each battle. She usually makes it a 20Q quiz so lets say 4 battles, 5 questions about each. She also says some can have a humorous answer, but the questions have to be legit. When they bring in their homework the next day lets say one of them didn't do the homework he has to take one of the quizzes and take it as an actual quiz and will get graded on it accordingly out of 20. The others will have a homework well done! This method teaches my whole class the best. Maybe you could do it for once every chapter and lets say the chapter has 4 lessons, ask 5 questions per lesson.
Now, about the apathetic students. I'm one of those kids, but only when it comes to English class. I will put my head down and sleep the whole time everyday for English. I simply have no enthusiasm for the subject. This is due to the fact that I have one of the worst English teachers. She is terrible because she is so monotone and bores everyone to death. You're a young teacher so I recommend cracking jokes sometimes and having energy, but that sometimes leads to kids getting out of hand.
Lastly, honestly the best way to make kids enthusiastic is an incentive. You said don't do the work for anyone or your grade, but kids only want something. I find the best incentive is a nice, big, long, juicy
Sour Belts.