Carburetor Issues

1931 McCormick-Deering 22-36.
I want to pose a couple or more questions:
1) When my throttle is fully open, the butterfly is less than open fully. I am taking it that this must be normal because, in one of my images below, what I have labeled as "2" is pegged when the throttle is fully open (butterfly not fully open).
2) In NO diagram that I have of the carburetors for this tractor, do I see the screw, pointed to by my arrow, pictured or described. As best I can tell, this screw should act as a stop for the idle position of the butterfly. In my carburetor, the end of the screw was eaten away. In my image, what I have labeled as "3" would be pinned against the end of the screw at idle, yes?
3) When "1" is pegged against the post, the butterfly has gone PAST CENTER, which does not seem right.
Could someone please help me with the interpretation of this?
Thanks,
Tom
P.S. Unfortunately, there is nothing in any of my literature and I am not a genius with carburetors.
<a href="http://s414.photobucket.com/albums/pp223/tschulein/?action=view&current=Throttlestopscrew600.jpg" target="_blank"> </a>
<a href="http://s414.photobucket.com/albums/pp223/tschulein/?action=view&current=Number2pinnedonpeg600.jpg" target="_blank"></a>
<a href="http://s414.photobucket.com/albums/pp223/tschulein/?action=view&current=Number1pinnedonpeg600.jpg" target="_blank"></a>
<a href="http://s414.photobucket.com/albums/pp223/tschulein/?action=view&current=Butterflypastcenter600.jpg" target="_blank"></a>
<a href="http://s414.photobucket.com/albums/pp223/tschulein/?action=view&current=Asfarasthrottleopens600.jpg" target="_blank"></a>

start with easy first:
answer to 2nd question is yes.
answer to 1st question is i am thinking the same as you. because these engines only ran about 1100rpm. was thinkin may be the shaft might be twisted, but not sure.
answer to question 3: this is correct as at idle the butterfly is almost closed and is held from closing with the screw in 2nd question . otherwise if it closed completely tractor would stall.

No, I have a regular carb in my hand and the throttle plate in it does not open fully neither. Must be the way they are made. Yes, the screw is the low idle stop.