Great tips, thanks! It's weird, as the images I set to be featured images show up in the debug tool - but they still displayed incorrectly when I published. Don't understand this. I changed the image size (smaller, actually) for my last post yesterday, and it worked properly. Not sure why. In any case, I have 2 other questions for you.
1) When I go to the debug link, I see the following errors:
Like Button Warnings That Should Be Fixed
Admins And App ID Missing: fb:admins and fb:app_id tags are missing. These tags are necessary for Facebook to render a News Feed story that generates a high click-through rate.
What does this mean? What do I need to do in WP, if anything?
2) Separate question: is there a way to add an arrow button or 'go to top' button on my individual posts, to make it easier/faster for viewers to scroll up? Some of my posts are quite long with images, etc.