Can I use me being a victim of identity theft as A tax write-off. I had to pay child support for a kid . I never had any kids

No there is no "write off" for being a victim of identity theft.  There are no deductions for casualty losses or thefts since the tax laws changed for 2018 and beyond, unless you experience a casualty loss in a federally declared disaster area.

And child support is not deductible.  Sorry.

Child support was deducted from my account . I do not have any children.  

Unfortunately, as xmasbaby0 explains above, there’s no longer a deduction available when you’re a victim of a scam like this, whether the child was yours or not.