best to read this article from the IRS; you situation is right on the cusp of the tax law change that was effective Jan 1, 2019. it will come down to the definition of the word 'executed'...... I imagine this was discussed with your lawyer, etc at the time the payments were negotiated - did you ask your lawyer?
https://www.irs.gov/forms-pubs/clarification-changes-to-deduction-for-certain-alimony-payments-effec...
