There are a few reasons that I stay in contact with him....but mostly (I know this is bad) but I like to rub in that I am so happy in my new life. I try not to make it obvious, but I like him to know that I have moved on to better things. Also, I am nosey and I can get info about him and my cousin. I know I shouldn't care what they do, but I cant help but be curious.

When I read that paragraph ,, only one thing came to mind ,,,,,, Curiosity killed the cat .

O ,,,, O ,,, another one >>>>>....Let sleeping dogs lie .

Now just my guess ; >>>>. May be while your first argument went on ,, and you answering his questions " honestly * ,,,, He may have been perceiving this as his worse case scenario .
He may have had a thought about your ex , and your contact with him ,, Your Husband might have been leaning in the direction that you said * Hi * to your ex just in passing ... [ the other end of the spectrum ] .

IMO .
WMD.