From this site I know of a few other stories that contain facesitting and are hard to find through search engine. One of them is this one: Descent into oral servitude
Its long and mainly talks about forced cunnilingus but with a lot of facesitting positions (with a queening chair being my favourite ).
You might also want to check out other stories from that author (krr1957) especially Syracuse is waiting.
There's also another nice incest facesitting story here Making a slave.