I looked at your materials and it seems what you did is create an image frame on each of the facing pages. They bleed .125 on the top/bottom/outside, but end .125 inside the gutter. Correct so far?
No, there are actually 2 InDesign Files, Layout.indd and Export.indd. The corresponding Layout pages are placed on the Export pages. The Export layout has the gap created in the master spread and you would edit the layout version then simply update the Export version. You can place InDesign files in InDesign files.
So here I've added some crossover text. Export on the left Layout on the right:
Here are the sample files updated:
http://www.zenodesign.com/forum/IngramTest2.zip
Again the printer shouldn't be forcing you into this kludge—you should never have to build a bleed into a document. The only exception might be Wire-O where the inside edge actually gets trimmed.
Any imposition software I've used lets me set a gap plus creep during the imposition. They should be asking for no interior bleed and adding the white glue space in the imposition.