I wasn't able to download your modified XML file, but when my browser attempted to display the file directly, I got an error stating that an invalid character had been found in a text string. So I suspect the problem you're encountering isn't with any limit regarding how much text can be displayed, but rather, is with a character in your text that's aborting the display.
My best guess would be that you've got an ampersand (&) in the text, as I know for a fact that ampersands will abort text displays. I discovered that while working on my Help window mod.
Replace any ampersands in your text with their HTML equivalents (or just with "and"), and see what happens.
-- Darryl (Milquetowst, et al.)