You can never claim your wife as a dependent. Filing jointly gives you all the benefits of having the additional person.
Whether you owe tax or get a refund is not based on a specific amount of income. It depends on how much tax is withheld from your pay, compared to your total tax for the year. The amount of tax that is withheld is determined by what you put on the W-4 form that you give to your employer. If you both work you can use the Tax Withholding Estimator on the IRS web site to figure out what you should each put on your W-4 forms. It will show you how to adjust your withholding to get the approximate refund amount that you want.
