The endnotes are fundamental to the experience. There are some key plot points divulged or hinted at there first (and sometimes there exclusively, IIRC). Pemulis' funniest moments are back there. I still find my mind drifting to the description of Cage III: Free Show from J.O.I.'s filmography from time to time.

If nothing else, I once read a comment somewhere online that noted that the constant back-and-forth from text to endnotes and back is physically analogous to a back-and-forth in a tennis match. If thematic consistency in the third dimension was actually something DFW was going for, it's a shame you're only seeing half of the court.

DFW said somewhere (I can't recall where) that he wanted the reader to have the physical experience of moving back and forth, and that the process of moving and flipping sort of echoed the jumping between the years of the chapters and story. Or something :)

I found it annoying initially, but after I read that (when I was maybe 1/3 through), I did come to appreciate it a bit more. Maybe I'm just impressionable.

Cut the book in half, literally. Or even just cut the footnotes out and make them a separate book.

Yeah, or read it on a Kindle like I did and the jumping is pretty easy.