(1) The rear guard screws are the same length. The M'03-A3 front guard screws are 0.1" shorter than M1903 front guard screws.
(2) a. No.
(2) b. To some extent.
(2) c. By the length and slot.
(3) Yes. As I recall, Benrus Watch Co. may have been one of the contractors. But, I would have to consult my records to be sure.
(4) March, 1918, at RIA. December, 1918, at SA.
Hope this helps.
J.B.