Love the LC series, by the way :)
Johnny is correct on both fronts but I'll add a bit more info.
Your FSA is limited to $5K, and pre ALL tax. So you have to factor FICA into the mix. However, it might not be clear cut for you at 7.65%. You used 28% in your calculation, which indicates high income. If your wages exceed $118K/yr, you max out your Social Security at the top of that wage base. This means even if you get this deduction pre-tax, you might not benefit fully from the reduction in FICA tax. If your taxable wages > (118,000 + 5,000) or $123,000, you might only benefit as follows by using the FSA:
x 28% (Fed) x ?% (State/Local) x 1.45% (Medicare)
After that you should use the dependent care credit
. As johnny mentioned, it's a credit not a deduction. You will receive 20% back below your income tax calculation (it's as if you paid in extra federal withholdings). Since you are already maxing out the FSA at $5,000, and the limit is $6,000, I would advise putting $1,000 on this form. You can claim expenses here that weren't reimbursed by an FSA.
It gets even more complex than that though, and this is the real reason why the FSA should be maxed: It lowers everything. FICA wages base, taxable wages on W-2, which in turn reduces your AGI, which in turn can increase other deductions/credits you aren't getting (like the child tax credit, although you may be phased out of that since you are in the 28% bracket, but with enough work you might be able to get this and other benefits). It also lowers any taxable income on a state or city tax return since your taxable wages (Box 1 on the W-2) will be lowered by the FSA withholding. The dependent care credit is a federal credit, and I know my state doesn't have a similar one.
Max out the FSA. It's worth it. If you are still unsure, send me a PM with the numbers and I'll let you know exactly how much it benefits you.