Am I remembering correctly that mu or alarm points are on extraordinary vessels? Is this always the case? And are source points also on extraordinary vessels? Or are they simply a "reservoir" within the acupuncture meridian that sends qi directly to the organ especially when stimulated?
No that is incorrect. You should probably start by reading the acupuncture point categories page and click on the "detailed theory" links for the sections are you asking about. The basics are presented within those sections.
Generally utilization of the extraordinary vessels involve the master/coupled points. Mu points are on the front of the body on regular meridians and shu points are on the back of the body. The Mu and Shu points can be used together within a treatment, but not necessarily. And I'm assuming by source points you were referring to the shu points - perhaps not. Either way, source points is another theory altogether and is explained in the detailed theory section.