Mr. Donald asked me a difficult question - Page 10

Let us see this theoretical combination where the shoulder blade is less than 45 degrees and front upper arm angle remains the same.

Dog in standing, shoulder angle is 35 (maybe not possible in reality but for learning purpose).

Let us look closely at the shoulder of this case, shoulder angle 35 degrees and compare the outcome to the ideal case of shoulder angles 45 and 53 degrees.
Now the sum of angles of shoulder angles is 88 degrees. The sum of bone lengths is 38.7215 cms with an increase of 2.7 cms or 7.5%, also front upper arm length got bigger and shoulder blade length got a little smaller.

Let us see what happens to the reach, it got better 44.94 cms with an increase of 1.7 cms or 3.9%.

What still hold correct

As the shoulder angle gets smaller, front upper arm remaining at ideal of 53 degrees, the sum of shoulder angles becomes less, the shoulder blade length gets very slightly shorter, front upper arm length increases valuably, sum of shoulder bones increase valuably, the front reach increases valuably.
Proportion of shoulder blade length to front upper arm length is 1:1.36, we notice that the proportion increased while still the front reach incresed so the assuption or deduction that the less the proportion the better the front reach is wrong.

Still holds correct

Less shoulder angle better reach
Less shoulder sum of angles better reach
Less shoulder angles more sum of bone lengths
More shoulder bone lengths, more bone lengths of front assembly, better front reach
 

I see it is too difficult for me to deal with various analysis elements, so I will only comment on the most important effects and later make charts of results for each element of interest and see the common relation (trend).

Let us see what happens when the shoulder angle increases.

Standing, shoulder angle 50, front upper arm remaining 53

Let us look closely at the shoulder

Corresponding reach

Looking at the shoulder the sum of shoulder bones is 34.7557 with a decrease of 1.244 cms or 3.45%  , comparing to the ideal shoulder where the shoulder angle is 45 and front upper arm angle is 53 degrees, the sum of shoulder angles is 103. The ratio between the length of shoulder blade to the front upper arm length is 1: 1.06.
The front reach decreased 0.95 cm or 2.2%.

Let us see what happens when the shoulder angle is bigger

Standing, shoulder angle 55, front upper arm angle remaining 53 degree