My W-2 doesn’t have Federal Income Taxes withheld but it does have a section for FUTA. Why is this? And should I be worried about the FIT being blank?

Federal Unemployment Tax(FUTA) tax is separate from Federal Income tax, and social security and Medicare taxes (see https://goo.gl/cGyhkR). FUTA is a requirement for employers from their own funds, but may be reported on your W-2 for reporting purposes. 

Yes, you should be concerned if you find you owe Federal Income Taxes(FIT). FIT is withheld depending on several factors, including your income reported for the payroll period and what you selected on the W-4. Therefore, you may or may not have FIT withheld. You cannot change the withholding for 2017, however you can going forward for 2018 by submitting a new W-4 form to your employer:  https://ttlc.intuit.com/replies/3301783