1. Sorry, Child Support has never been deductible. Alimony paid used to be but no longer is. Alimonies for divorces and separations finalized after 2018 are no longer taxable or deductible. See Tax Reform
https://ttlc.intuit.com/community/tax-reform/help/how-will-tax-reform-affect-my-federal-tax-return/0...
2. You file 2019 as Single. Your filing status is based on December 31 of each year.
