Many questions

Last night, I watched most of Star Wars, episode III, Revenge of the Siths. It was the first time I saw more than a half hour of a Star Wars movie and actually followed the plot. Because this was my introduction to the series, I had a cornucopia of questions as I was watching. I began to pester Josh. Why do Anakin and Padme have to keep their baby/marriage a secret? Who's the guy Anakin and Obi Wan are fighting and why does the old guy ask Anakin to kill him? Why is there a weird recurrent arm cutting theme? I know giving Darth Vader the respirator is a climactic plot turn, but shouldn't they have given him the respirator right away, even before operating on his limbs? Etc.
I found many of the answers on Wikipedia. They have the keep the baby a secret because Jedi's aren't supposed to marry or fall in love. (This generated an unanswered question, how are the Jedi to perpetuate their race if they can't marry/reproduce? Especially if the Jedi potential is hereditary. Or is it trying to say Jedi's can only have one night stands?!) Anakin and Obi Wan are fighting Count Dooku, a Jedi that turned to the dark side and became Lord Sidius's apprentice.
This morning, as I was riding on the train with Josh, I blurted excitedly, "I know why there's an arm cutting recurring theme! It's a deliberate attempt to prevent the person from doing the force lightning!" I got chastised for being obsessed and geeky. Shut up, he said. Don't talk about Star Wars any more. He treated me as if I was an I-CON (which is different from ICON) card carrying weirdo. But I ignored him and continued..."Or can you do a force lightning with a robotic arm?!"

UPDATE: Greg from work answered all my questions. He scorns the 2nd trilogy so I'm going to have to watch the 1st trilogy to see for myself.