Your family has been lifted up in prayer. It is definitely a tough decision to quit a job when you believe your family depends on that income to live. However, it is not the income we should depend on, but Yahweh Himself. I firmly believe that Yahweh will bless you for your desire to obey His Sabbath command. He gave your wife that job in the first place and can easily replace that income through other means. I'm sure there are many Sabbath keepers that can testify of Yahweh's faithfulness in blessing them under similar circumstances.
May His peace and providence sustain you even in times of financial difficulty.