I don't really trust Jeffrey Long and his NDERF site. He seems to exclude most other countries' and NDEs that include non-Christian visions like Hindu Gods etc.
That's a fair point. How do you know this? Clearly there's money to be made if both Jeffrey and his wife are writing books and profiting from people's experiences -- no harm in that, but later on we read:
"If you have benefited from our work and NDERF.org, consider a monthly or one-time donation through our 501(c)3 non-profit organization. We Really Need Your Help. Click here for more information."
He has said in an interview that he has seen no evidence of polytheism. As far as your link to Islam that describes the religious beliefs. It isn't a list of NDEs that confirm Islam beliefs in contrast to Christian ones. Seeing Mohammed or something.
I don't think it matters whether it is 8,9,10 etc. In theory, it could be >8, but perhaps it requires a greater area to work with, so 8 is optimal. Not sure, though