I did a quick literature review search. The relationship between divorces and education may be related to age. Those with a higher the education generally marry later in life as compared to a person with limited education.
Witnesses tend to marry very young (I was 19 years old in my failed marriage). And of course we know the reason. The sexual drive is very strong and the context of the religion is that sex outside of marriage is very bad. So, if you want to have sex you gotta get married.
I suspect that divorces among witnesses is pretty high. The dilemma is that a divorce is generally associated with a disfellowshipping. And if you are disfellowshipped, you are no longer part of the congregation, so your numbers don't count.