This might help, somewhat.
A link to a well known PS:T Fan Site, main site linked below:
http://torment.db-forge.com/

Now, about the cap, the rumor here is....
Quote

From the link here on The Pit's PS:T FAQ:
http://torment.db-forge.com/armory/hints/faq.shtml#1

Is there an experience cap?

No, however, Huggies_Dragon informs me that the Nameless One no longer accrues experience points after 12,000,000. Besides, don't you have better things to do?