APM Citrix tidy session termination

Yes, you can modify your existing iRule to whatever delay value you would like. However, it sounds like you want to modify the APM policies idle timeout value rather then the iRules delay timer. The only purpose of the irule is to terminate the users APM session when they log off the Citrix WEB server. In some cases, the behavior of the irule is not desired and can be removed. Check out the properties page of your access policy and you will note a 900 second idle timeout value, modify this value to match your web interface idle timeout value.

It surprises me that you had trouble with the new iApp, did you apply the template to your existing iApp deployment or create a separate iApp instance?