generating index on large document

I have a 2500 page document that is taking 6 hours to generate. It's a custom bookmap with maprefs to topicrefs.

I have 2 issues:

1. The length of time it takes to generate the PDF:
   Is there a way to break up this document and still get a full index with correct page numbers? 
2. The styling of the index is messed up halfway through the index.
   We have been generating individual indexes for each document and the index looks good. Once we compiled the full book/PDF, the styling was all messed up. Our deadline to finalize content is next week. Note we have approx 142 topicrefs, broken down into approx 20 maprefs. Also, note, we used PE 7.0 to generate the PDF. I am currently testing with Styler to see if there's any improvement.

Can anyone help or offer advice on how to handle this large document or why the styling of the index is all messed up. I am attaching a screenshot of the index.

I can live with the 6 hour performance, however, I really need to fix the style.