There are several tax prep services that will let you prepare your return at no cost to you.
At least one will even file your Federal return for you at no cost to you.
Try different tax software and enter your deductions and social security.
If you get the same results (tax due) then you can figure that your particular situation is well understood by the tax software.
NOTE: when I did this for my unrelated situation, out of four software packages, I got four different results, all wrong, which was rather disconcerting.
Later, one updated their software - twice - and finally calculated correctly.
Hint: it wasn't TurboTax Online.
