You have real problems ... if YOU took a distribution from YOUR 401K then you need to pay taxes on the entire distribution on your tax return no matter what you did with the money or what he did with it. YOU did not roll the money anywhere ... you gave the money to him. Since you did not roll the money into an IRA in your name do not say you did in the program.
To keep you from paying taxes on this amount this should have been done as a QDRO as part of the divorce decree ... the judge would have issued a QDRO to your 401K manager to issue a payment directly to him and the 1099-R would have been issued to him so you would have nothing to report. Seek legal council before you do this again.
