To keep a backup copy of you Blogger blog on your hard disk go to Settings > Basic > Import Blog. See the yellow circles in the screen-shot below. Click on import and give a meaningful name and date to the saved file. When ever you want to restore your crashed blog select the downloaded xml file and upload it.
To backup your template go to Layout > Edit HTML > Download Full Template. Save this file in similar manner. Kindly note that both the files (the blog backup file and the template backup file) are in xml format and do not have a comprehensible name. It is easy to get confused between the two so make sure you do have some marker as blog and template either in the file-name or in the folder name to identify them later.
