Hi,
I'm actually facing the same situation. I didn't really try too hard to get pfSense LB working with sticky connections properly, so what I ended up doing was using the session clustering of tomcat instead. Works quite well actually. The biggest catch is that all you session information must be serializable. The added benefit of clustered tomcats is that if you need to restart one tomcat, you don't lose any of the sessions.
I know this doesn't answer your question, but thought it might give you another avenue if you can't get hte LB working as you wish.
Good Luck. Let me know if you end up getting it working.
Thanks,
Eric