Yes, he was a wing half, so therefore a midfielder. Of course, he might have moved back as he got older and more experienced. Having said he was a wing half, he was actually a left half, the number 6. I don't know how much teams were going for four at the back as early as 1958, but my memory...
No certainty that the three West Ham would have made the team. Moore very probably, but the other two less probable (although many things might have moved on in an 8 year gap; Ramsey might not even have been the manager, for example).
We might have done better at the '58 and '62 ones too - remember, Duncan Edwards wasn't the only England international we lost. Tommy Taylor was a brilliant 'old fashioned' centre forward, Roger Byrne was captain of United and lined up to succeed Billy Wright in the England job, and Mark Jones...