The law firm is what is referred to for QBI purposes as a specified service trade or business (SSTB). the calculation differs for a SSTB.
you'll need to review form 8995 or 8995A (read the top of the form to see which to use). if you are using online you'll need to pay your Turbotax fees before you can review the form
here's a link to the federal form which you might want to complete manually to see the results.
however, if you are filing other than joint you get no deduction if your taxable income before the QBI deduction is over $241,950 for joint the amount is $483,900
https://www.irs.gov/site-index-search?search=8995&field_pup_historical_1=1&field_pup_historical=1
note that for the law firm net income, QBI would be schedule C net income. less 1/2 your SE tax. less retirement contributions based on the income. less any deduction for self-employed medical insurance
