Complex set of questions that can't be answered as easily as asked. I'll try to address a few in brief, and hope that SSTI member/experts Sue Deppe and Dave McShane will add their greater expertise.
Best place to start might be with the idea that all religions address a range of issues that matter most to us humans, issues that have concerned people in every era and every locale. These issues (among which are the concept of the meaning of life, the meaning of death, responsibility for children and dependent others, questions about the origin of everything we cannot easily explain, etc.) all involve intense affect that is handled in each of us by what Tomkins called an Ideological Script. These scripts are central to the affective life of each of us, are relatively immutable, and are extraordinarily powerful. I suggest you click up to the hyperlink for the Tomkins Institute on the BOL home page, thence to the articles from our Bulletin, and print out the paper by Stone and Schaffner on the Tomkins Polarity Scale. Take it yourself to get a sense of the power of the issues addressed in this psychological test, and consider how much you might be able to predict the responses of people who live in various religious systems. Religion is very much about systems of Stimulus, Affect, and Response codified in ways that allow people to group for reinforcement and continued enhancement of the skills associated with the ideological scripts common to that group.
All of my friends who worship in Pentecostal systems seem quite within the range of normal outside the devotional experience you describe, which certainly would make me believe that the religion is neither an excuse for psychiatric illness nor an inducement to madness. Rather, you can view the SARS (stimulus-affect-response sequences) involved as a form of trance behavior into which each individual has agreed to enter, and which each leaves when the experience is declared over. There are lots of places and events we adults attend in order to experience high-density affect limited to that venue; think of the mass expression of a wide range of affect during sporting events or rock concerts for one example.
Remember that I characterize the affect system as something analogous to a bank of nine spotlights, each a different color, each flicked on by a different kind of switch, each illuminating some triggering source in its own way, forcing us to pay (conscious) attention to that source in the precise manner dictated by that beam, and then turned off as soon as that attention has initiated the process made necessary by it. We view psychopathology as the set of conditions in which any part of this is made impossible. Entertainments that allow me to experience and express excitement at a level and duration normally forbidden by commonly accepted cultural rules are worth their tariff. Those who remain equally excited outside such venues may be assessed for the possibility of a defect in affect regulation, which defect may come from hardware (as in Bipolar Illness) or from software (a script that makes one skew to the rest of us).
I don't see any evidence of psychopathology in the religious observance you describe, and I suspect that those who gravitate toward it do feel immensely gratified by the measured and time-limited experience of both positive and negative affect it affords. The normal affect system has a clearly identified OFF button, and I think that most religious systems take care to turn off high density affect before their parishioners leave the hall. As for the fraction of their net worth contributed by people to their religions, I would suggest that throughout history no system of worship has been entirely free of sociopathic leaders, despite that the overwhelming majority of religious leaders make great personal sacrifice in order to serve the ideologies they find meaningful.
I'm sure we'll read a number of additional responses to this important question.