After a few days away from my project, I went through and edited yet again.
I removed several images, re-arranged some sequences, and cleaned up the text. I also was able to improve the image quality of the finished PDF while still keeping under the 15mb limit. After several tests, I found that having the maximum quality setting on JPEG export from LR and the maximum quality setting and 100dpi on the PDF generate setting in InDesign gave me the best tradeoff of tonality and resolution in the finished PDF.
The link is here for ISSUU reading:http://issuu.com/georgecpappas/docs/route15