You can only create shortcuts on the home screen from Safari. They are for websites. You can't make one for a file.
Your ability to view the spreadsheet in Mail is through QuickLook, which is view only and will not save the file of itself. Instead you'll ned to download another app to view or edit the file. Once you do you'll get an Open In option when viewing the spreadsheet in Mail. This copies the file to that app, where you will view/edit/whatever.
What app you should download depends on how you need to use the spreadsheet, and how cross platform compatible you need it to be.