J W's strictly obey the scripture Matt. 5.31-32 No divorce "except on account of fornication"...
If one lives in country where no divorce is ever allowed for any reason, you may get approval for a common law arrangement , if you can convince the elders that your ex has committed fornication.
If I read it right, your father wants a divorce that would allow his zealous dub new partner to marry him?
he can , wait and hope that ex wife does him a favour by taking a new man?
Seduce his new partner, so his first marriage is broken and ex wife divorces him. Then throw themselves on the mercy of the congo..?
explore the variations on a theme of "fornication" which is not entirely the same as adultery?
Make up with the ex? make up his mind to be celibate? Forget it and look for another partner? BTW If he is not a true believer
is , then the relationship is very difficult.