plugin_init() is run when the plugin is initiated. Cvars should be set in plugin_cfg().
If you are having issues using Ham forwards, you should look at existing working plugins that use the functions you are interested in. You are using RegisterHam() incorrectly. If you look at the include for Ham (hamsandwich.inc), you will see that the second argument is the EntityClass, not the function you want called (which is called the "callback").