You do have secret reserves, as per the PM events and whatnot. Yeah, you can Burn your ghouls into nothing.
Why yes, you can share mana. For everyone NOT in your party, it requires physical contact. Since you are a party with experience and history together, you can indeed Energize any of your fellow party members. It'll come at a cost of MP to the sender, of course.
I'm just gonna borrow from Steven King here to explain that concept:
KHEF: Literally speaking, khef means "the sharing of water." It also implies birth, life force, and all that is essential to existence. Khef can only be shared by those whom destiny has welded together for good or ill—in other words, by those who are KA-TET. Khef is both individual and collective. It implies the knowledge a person gains from dream-life as well as his or her life force. Khef is the web that binds a KA-TET. Those who share khef share thoughts. Their destinies are linked, as are their life forces. Behind the multiple meanings of this word lies a philosophy of interconnectedness, a sense that all individuals, all events, are part of a greater pattern or plan.
KA-TET: Ka-tet means "one made from many." Ka refers to destiny; tet refers to a group of people with the same interests or goals. Ka-tet is the place where men’s lives are joined by fate. Ka-tet cannot be changed or bent to any individual’s will, but it can be seen, known, and understood. The philosophers of GILEAD stated that the bonds of ka-tet could be broken only by death or treachery. However, Roland’s teacher Cort maintained that neither death nor treachery were strong enough to break the bonds of ka-tet, since these events are also tied to KA, or fate. Each member of a ka-tet is a piece of a puzzle. Each individual piece is a mystery, but when put together, the collective pieces form a greater picture. It takes many interwoven ka-tets to weave a historical tapestry. Ka-tets overlap, often sharing members. A ka-tet is not always bound by love, affection, or friendship. Enemies are also ka-tet. Although usually referred to as positive or at least inevitable, the forces of KA and ka-tet can sometimes cast a sinister shadow over our lives.
As a note, the Corpriests can share mana among themselves. The Shinpriests can as well, but the two groups cannot share with each other. The Corpriest and Shinpriest are close enough, physically speaking, to touch and share mana.