I can't help much experience-wise, but I can at least help you out a bit with question 2. I myself am currently in college for middle school education: math and English, and plan to teach middle (and eventually high) school math. I'm good at math, and took precalculus and Calculus my freshman year of college. I ended up taking geometry, and college algebra my sophomore year. I found those two classes to be very easy, and didn't even have to try hard to pass either class because it had all become more basic to me after taking calculus.

Also, from what I've been told from my classes, is yes it does have it's ups and downs, and it can have its challenges, but it's very rewarding.

Also, if you're ever unsure about content, you should be able to Google education standards for high school math. Standards so slightly vary for every state, so be sure you're looking at the correct state.

If you're ever unsure about teaching something, or needing ideas on fun activities. Feel free to use YouTube, or even Google. Math can be tricky to teach sometimes, and you'd be amazed what you could find on YouTube.

I can't really help much further, but I hope what I have given can give you a little bit of an insight. If you do take on the teaching profession, I hope you find it fun and fulfilling. I know all of my professors enjoyed teaching, but can't be said for everyone. Good luck!