1) Go to Appearance > Menus and just drag and drop items into levels you need. For the first level choose mega menu design. If you provide me temporary access to your Dashboard I could help you to create an example.
2) There are no more labels and it’s possible to implement only by additional customization if you have PHP skills. But you can rename existing labels using translation files if you don’t plan to use some of them.
3) Go to Theme Options > E-Commerce > Single Products > Enable title above the price > On.
4) Use translation files http://xstore.helpscoutdocs.com/article/30-base-theme-translation and just translate the necessary strings to what you want to have instead of SKU, it will be easier than change files.