Also, you can run Tomcat with JAVA_OPTS="-Xprof". That will cause Tomcat to dump a basic execution profile into catalina.out upon shutdown. So what you do is start Tomcat (with the -Xprof flag for Java), run the load test for 10 minutes and then stop Tomcat. Finally open catalina.out in your text editor and see what the profile tells you.
For the thread pools, have a look at http://java-monitor.com/install.html
and follow instructions. That will give you performance graphs of your servers, such as the thread pool fill levels.
Please note that this slows Tomcat down a bit, but the result may be worth it.