Please use the "code" tags when posting source code or XML text - I edited your post for you to include the tags.
I'm not sure what it is that you are asking. According to the *-ds-xml file you posted, JBoss AS will create 5 connections in the pool the first time your code asks for a connection. And will create at most 20 connections in that pool. Why do you think that multiple pools are being created (posting the "suspicious" log message would have been helpful)
The suspicious log message is 'Creating XA Pool' (thousands times) - I suppose the pool is not persistent. Database monitoring says that there is login before executing every query, and logout after it.