This is possible using code with Infopath and the Excel ActiveX object (only way I can think of since you have everything in a Document Library). It will take a while since you have so many forms.
You will have to design a form to export all that info, and will have to run in batches so Infopath doesn't go cre-azy nuts as it approaches 500M of memory (Infopath2003/2007 literally stops around that mark, it's got a nasty memory hole and it leaks badly, 2010 is better, but it has the same problem)