Is it permissible for a wife to take her husband's money without his knowledge, justifying it by circumstances, then refuse to help him with it when he is in need?

If the husband spends on his wife in a reasonable manner, then she is not entitled to take anything from his money without his permission. If she does, she is transgressing and must return what she took, unless he pardons her. The relationship between spouses should be based on affection, mercy, and understanding.