Know the number of pages printed from cups printing

Check out PDFsam: a free, open source utility for (you guessed it) splitting and merging PDFs. You may be able to script it to get it to do what you want.

Your application seems to be confused about whose responsibility it is to determine the rendering of the document. That it precedes the document with an SI character suggests that it is trying to control the rendering itself - [SI] selects condensed mode printing on an IBM DMP (required for 132 column printing in portrait layout). Assuming that your printer is configured and supports IBM emulation, then its simply a matter of setting up a new device in cups using the generic ASCII driver.

If your printers do not support IBM emulation, and the generic driver does not work as expected, then you'll probably need to strip the [SI] from the file. See this document for details of how to write your own filter. It describes the process for a DVI file - but the principle is the same: first invent a mimetype for your files, say application/vnd.local.proprinter, then set up a recipe for mapping the 'magic bytes' to the mimetype (see /etc/cups/mime.types) then write a script to strip the leading [SI] and convert to ps (man a2ps).