Answers are as follows:
(1) Your rifle was probably shipped in late December, 1943, or early January, 1944.
(2) Get some Birchwood Casey Water-Base Walnut Stain, dilute it down with water until very thin, then apply to the stock in steps over a period of time until you get matching darkness. If the stock is coated with oil, then you may need to use some odorless mineral spirits to dissolve the oil and get down to bare wood that will absorb the water-based stain.
(3) I speculate that the stock discoloration doesn't de-value the rifle more than 20%, if that much.
Good Luck! And thanks for sharing!
J.B.