Your federal withholding has nothing to do with your tax liability. Your tax liability is determined by subtracting your standard deduction ($12,000 for single) from your adjusted gross income ($85,000 if you have no adjustments to lower you earnings) and calculating how much tax you are liable for on the remaining $73,000 of taxable income. According to my calculations using the 2018 marginal tax rates, your tax liability will be $11,046. Since the tax liability is more than the $7500 of electric vehicle credit, you would qualify for the entire credit. Your withholding as determined by your W-4 will affect how much refund you get but it will not affect your qualification for the credit.
