What Bible was John Milton using as a source?
In all likelihood, he used several. He was extremely well-educated for his time, and clearly had access to church libraries. Furthermore, he was not one to just tow-the-line, and so he was not afraid to incorporate various ideas. Probably more informative for your research would be to ask what sources besides just bibles that he used. Look for earlier theologians for the basis of his concepts, and medieval catholic mythology for characters/storyline. But my best recommendation is just search for a Milton scholar at an ivy league lit or history department, and email the person. They get so little attention from the outside world that they would probably quite appreciate your interest and flood you with info.