How to change a specific thumbnail in a Recent Posts Widget

I am using Jetpacks Top Posts and Pages widget in my sidebar and it is working great except that for my online store it is pulling my gravatar image versus an image I have inserted as a featured image and in the Open Graph Settings.

You can see it on this page on the right in the sidebar:

Also, an unrelated question is regarding my Newsletter sign up on the right at the top of the sidebar and at the bottom of the article.

The word "Submit" is not showing up any longer. I don't see where I can change the css to make it appear again or if it is a plugin issue.

Thanks for you help!