1- You have to stand normally as you usually do. Don’t try too hard to put them together or spread them apart. The feet must not be more than 4 fingers apart from one another. Some people spread their feet apart too much.
2- al-Afuu- there is no difference. It goes back to Arabic grammar. If you are continuing and not taking a pause you can say al-Afwa al-Afwa
If you are stopping after each one you say al-Afuu
3- You have to try to recite it in the correct you to the best of your capabilities. Listen to how it is recited and recite like that. If you couldn’t then it’s ok.