Can't help with (1) and (4) as I ended up pivoting my career in a different direction relatively soon after obtaining my PMP (not great timing, I know, but one thing obtaining my PMP taught me was that legit, true-blue, by the book project management is incredibly difficult, often boring, and usually thankless!), but for the classroom hours, I would check with the Project Management Institute and see what they recommend in terms of suitable online options. You just want to make sure that if you go the Coursera route, that those trainings will count.
In terms of (3), it depends on a few factors. The intensive classes are expensive and have a reputation of being "cram-sessions," but by all accounts they do help you pass the test. If your company were paying for it, it would be a no-brainer. But when you're paying out of pocket I think the value proposition is less evident. I did self-study and found it to be completely doable. At the time, I had two small kids, but after they went to bed I did 1-2 hours of study, maybe 4 days a week, for probably...4-6 weeks before the exam? The only two books I used were the Rita Mulcahy book (legendary) and the PMBOK. I read and re-read all the Mulcahy chapters, made tons of flashcards, and took the quizzes several times each. I supplemented those with practice quizzes from the many online sites that share free questions. It takes some focus and commitment, but since I see this question often I always like to pop in and say that it's 100% a realistic option. As someone else noted, the PMP is all about how you would manage a project based on the PMBOK principles -- not necessarily how projects are managed at your company or in your industry. So you just need to go by the book, and you'll be fine.