Dating is legal after separation. Sexual relations is technically still adultery until absolute divorce is granted. Regardless of how long the separation has been, legally you are still married.
Adultery/criminal conversation is a misdemeanor and is rarely prosecuted…it’s just too common and most attorneys will not bother. I’ve read many posts on here about it but never once have I read that someone served jail time or fines for adultery.
My suggestion: if you have everything resolved and have been separated for almost the one year one day requirement…wait. Either the STBX has been making threats or it would bother you to know that you are doing something illegal. What’s a little more time, if you have waited this long?