Since you have EPP it implies that you have support contract. Have you already asked your question using our support channel? You are more likely to get targetted help there.
Your EPP bundle should aslo contain couple of examples that has complete info for getting started with a portlet using maven.
About compiling a portlet, you should be fine with the default JBoss classpath (as Eclipse WTP defines) plus $JBOSS_CONF/deploy/gatein.ear/lib.