If your ancestor uses the phrase "now wife" in his will, it does not mean that he was married before.
If Johann gives his farm to "his now wife and after her death to my children," it means his wife at the time the will was written. This was done to see to it that if this wife died and the testator remarried that the children and not the current wife inherited the property. Without the word "now," "wife" is vague. "Now wife" was done to clear things up, but it has confused many genealogists.