Speaking as someone who does come from the design industry (both web and deadtree, the former for 16 years, the latter for 20) I can assure you that the single element that is most responsible for readability is white space. Rarely, if ever, does readability increase when white space is reduced. The fact that you want to conserve pixels is irrelevant. The eye can keep track of two columns far better than three because you are decreasing the white space and simultaneously increasing visual 'noise'. My recommendation is to leave it at two and allow the reader to continue to scroll down should they wish to read them in their entirety.