​No matter how "kind" a toxic person may behave it is usually for a short period. They will always return to their baseline character and abusive behaviour.
A psychological abuser may go through a short period of being kind and staying off the radar but it would be for a reason of being caught out in a lie or facing some trouble with law enforcement, etc.
They will be super kind and nice to others around them either for purposes of minimising the abuse so that the victims around them can forget about it and focus on the adoration they are currently receiving or because they have stirred up some serious trouble and are in the firing line. Whichever the case, once this is over they will revert to who they are and the abuse will continue.
It is who they are, they do not know another way. Please accept this.
You are not the narc whisperer!
They will not miraculously change their ways because you have whispered a magic narc potion in their ears or sprinkled narc dust over their heads, waiting in anticipation for a miracle to happen.
This is serious and I need to to grasp the fact that your narcissist, abuser or sociopath is not going to change for you, or anyone after you.
The faster you acknowledge that you are literally dealing with a demon who is a soulless creature, the better off you and your children will be.
LEAVE! There are organisations who are able to evacuate you in South Africa.