Trying to using Rules to create page redirects to external links per node, but it's not working
Use the field redirection module. A great overview was provided by llulabot

https://www.lullabot.com/blog/article/module-monday-field-redirection

Mind you I've used Views with Conditional Fields to allow a single link to be either internal or external using a views template override when clicked (based on a radio button in the content type). Field redirection is easier to use than your custom solution.