How do I pass existing template variables on to an action controller?
Not really a direct answer to your question, but you could also perhaps remove the additional controller routing business and move your conditional logic into a plugin variable (or service method called from your variable).

{% if craft.myPlugin.everythingsOk(entry) %}
    // everything's ok, render template
{% endif %}


Your variable:

public function everythingsOk($entry)
{
    // Do some conditional checks

    if (craft()-&gt;myPlugin-&gt;doChecks($userId, $entry))
    {
        return true;
    }
    return false;
}