I think it’s best you show me a link to your site.
In the meantime, as for double images, my guess is that you are using a “Featured Image” plus an image inserted into the first part of the post? Recent Posts Plus won’t show thumbnails unless a post has a “Featured Image”.
As a side note, when someone starts to make changes to the theme’s core code, it falls out of theme support, but I will help you on this one. Please note that if I need to go in and fix the code, it becomes billable time, so you may want to be careful with custom code changes 🙂
But let’s start with sending me a link to your site. Also, did you see my post earlier about the double << you had in your code?
Also, you are correct, the Recent Posts snippet is not in the extras folder. I will need to add that and do an update to the theme.
Just to clarify, you are wanting your archives and blog (categories) to use excerpts instead of the_content method?