Re. relationships: The only people I've heard use "polyamorous" are referring to committed, marriage-like relationships involving more than two adults. There ought to be a category for those of us who don't want exclusivity with any number.

Huh. This is what I've usually heard referred to as "polyfidelity". The poly social circles that I'm familiar with encompass also (among others) people who have both "marriage-like" and "dating-like" relationships, people who have multiple dating-like relationships and no marriage-like ones, and people who have more complicated arrangements.

P(religion) also suffers from vagueness: what conditions would satisfy it? Not only are some religions vaguely defined, but there are many belief systems that are arguably relgions or not religions. Buddhism? Communism? Atheism?

The question is "What is the probability that any of humankind's revealed religions is more or less correct?"

"Revealed religion", to my interpretation, means "a religion whose teachings are presented as revelation from divine or supernatural entities". (See Wikipedia, where "revealed religion" links to the article on religious revelation.)

This would not include Communism or atheism. Buddhism (as usual) is complicated, since there are sects of Buddhism that make what sure sound to me like claims of revelation, while others sound more evidence-based. For that matter, it might not include Scientology, which presents itself as scientific discovery by human genius, rather than divine revelation, at least at the lower levels.