There's not a lot you can do w/ the attribute mistake. I've done the same myself and there isn't much you can edit and you can't delete from what I've seen. I ended up making the good one a favorite by selecting it and hitting the star icon. Then it's at the top right when you start and don't have to dig for it. 

Using the template is great when it works but everything has to be the same w/ the files you're importing. Do all the files have the same columns and column names? Are you choosing the same options beforehand like ignore consecutive delimiters etc? Every single thing has to be the same. Also, did you have your required attribute to import chosen before saving the template? Try it again with everything filled in and save it as a new name or save over the other one. It's normally one little thing, but it's never the same thing. (sorry for the lack of detail)