Thinking about telling OBS about ex-wife’s affair. Concerned about retaliation.

Long story short -

Am nearing the end of the divorce from my STBXW, who is engaged in an affair with a married man.

I have evidence that I think the OBS should have about the affair and the AP. Have been advised to wait until divorce is over.

I am concerned that my STBXW, once learning that I informed OBS, will take me back to court to modify custody (currently 50/50) of my son.

Am I overthinking this?