Your standard deduction filing single is the "LESSER" of $6,100 or your earned income plus $350.
This has nothing to do with a refund. You can not get back more taxes than you paid in, as shown on your W-2 in box 2. You are never refunded social security and medicare (boxes 4 and 6).
If your taxable income is zero, you'll get any withholding refunded back, but having zero taxable income doesn't give you a refund.
If the standard deduction exceeds your AGI, then Line 41 is zero, yes.