So is it certain that different spindle lengths differ the same amount on each side of the spindle?

If so, either 107 or 110 seem to be OK for a 45 mm chain line:

107 --> 47.5 - 3 (difference from 113 bracket on one side) = 44.5 chain line.
110 --> 47.5 - 1.5 (") = 46 chain line.

107 being "most ideal."