From Dashboard --> Settings --> BSK Column Posts, you may visit plugin BSK Column Posts setting page.
If there's read more tag in your post then BSK Column Posts will show content before if. For posts which have no that tag then BSK Column Posts will truncate posts content according to your setting. In BSK Column Posts setting page, you may enable "truncate posts content" and set the then of limited content.
When show featured images for posts the default size is thumbnail and you may change the default size or use size name which registered in your WordPress as shortcode parameter.