In my post above - I made a mistake on the link for the second news report - it should be:
http://www.deolhonews.com.br/testemunhas-de-jeova-mais-de-400-fieis/
though the above seems to have taken it from:
http://www.reconcavonews.com/2017/08/mais-de-400-fieis-desmaiam-durante.html
Has any of this been reported by news media outside of Angola?
My above -corrected- link (to Deolhon News) appears to be from a Brazilian news outlet? (ie, also Portuguese-speaking as per Angola)
Really though A LOT of 'internal' stuff from loads of countries does not get reported outside those countries.
Also, as no one appears to have actually died, it becomes less 'news-worthy' - but that's the nature of news unfortunately.
The known facts (Convention date/location) match up, the pictures also look reasonable.
The story WAS featured online by O Pais, which I believe is also a print newsaper in Angola? (so not just a one-person-blog)
I checked out the OP's link which was to a webpage that was merely repeating what O Pais said - basically O Pais appeared to the original source, which is why I linked to it in my own OP.
I also understand that O Pais featured the story on the front cover of their PRINT (?) version - as per below:
