We are very happy to know you like our theme SuperMag. Thank you for your feedback.
We are going to answer your query in points.
- AT Post Columns is widget designed for Widgets Area ( Home, Sidebar, Footer ), For working it to the inner pages, theme should be customize. We have not tested with those kinds of plugin, you are saying. We can suggest you to customize the theme using child theme or can order us for Customization http://www.acmethemes.com/customization-request/
- Recent Posts:- Without customizing SuperMag free theme, it is not possible for specific post. But in premium version SuperMagPro, news feed( News Ticker at header ), they can be display from specific Category( hence specific post )
- Your third query answer is already discussed here, http://www.acmethemes.com/supports/topic/remove-featured-image-in-single-post/
Theme functionalities and features can be added/customized using child theme. If you are interested in premium version, definitely it has more features.