Whoa!
Way too many questions for an old guy to answer- study the stickies more!
First mark is not a crown but an EG Eagle over the C/U.
Second eagle is the original proof eagle and was applied at Erfurt(Erfurt and DWM eagles are different, and the EG eagle is different yet from those).
Yes, the receiver has been re-numbered to match the frame, there is no reason to think the frame is from 1914- but it could be.
The suffix letter on the frame looks more like a "c" to me, but really need a couple more pictures.
Try side lighting and try to get rid of the bright spots.
The stamps on the right side of the receiver match up with #15 at this link:
http://www.lugerforum.com/lugermarkings/proof-2.html
So that would be correct for a 1914 DWM military pistol. Can anyone make out the "fraktur" letters on the receiver in my original post and tell me what they stand for? I found a chart but I'm having trouble reading them.,
#15 in the link are not from 1914- in 1914 there would be 3 C/S and the proof eagle; however- what
is on your pistol are the three C/S- which are correct for 1914!