Assuming you have not found the answer to this question.....
For each question.
Depends on your definition of useful or relevant. In most cases, knowledge that is generated is contextual to what it's been interpreted and used for, so you generally ask questions, like, for example, in terms of relevance: Which source is likely the most credible and less fallacious towards acquiring information. If you need useful sources on that, search The Hierarchy of Practical Evidence by Cedric Chin. For more scientific sources, there probably exists a much better method that I'm not aware of.
Three heuristcs helped me ranked information:
I can confidently say that I use the Barbell Method and The Time and Detail Heuristic intuitively when evaluating information.
Why do you suggest Calculus?