Point (3): I would ask the author to be more specific, unless the results are basic stuff. People have asked me in the past to add a theorem number or at least a section number.
Point (2) and (4): that's exactly what goes in your referee report. Point (2) is a minor change, point (4) is a major change. List them all and send them back in a nice list.
Point (1): I would point out briefly that the English needs a review; I think proofreading the English should be a job for mr. Springer or mr. Elsevier after acceptance.