Thanks for taking the time! An all you can eat Spotify like model removes all friction and allows me, as someone who loves to explore new content, to not have to worry at all about refunds or such stuff.
I am sure you are operating under constraints with the publishers but I do strongly encourage you to push for a fixed monthly model: by removing all "barriers to entry" of viewing an article, users can freely explore new content from new authors and publishers.
Regarding pricing, a song takes many man-hours to produce. Consider the man-hours that go into an article and the fact that a song can be replayed many times. Sure it must be fair but 0.25c per article is not sustainable for me considering the amount of content I consume.
I am subscribed to a number of magazines (Economist, Foreign Affairs, Private Eye and a couple of news papers) which I know I will read. But others (New Statesman, Spectator, FT) I only care to read an article or so a month; with a fixed monthly I can view all the publications using your service, with per-article pricing I would only consider you for the "long-tail" articles/publications. And frankly, I can safely assume that you much prefer that I read all the content on your platform...