At a chupah today, in the brocho of “asher yotzar es ho’odom betzalmo” a learned Rabbi said the word “binyOn” before “adai-ad” rather than the more usual “binyAn”. “binyOn” is the text in the Baer siddur. I was told that the word “binyan” cannot be construct in Biblical Hebrew with “adai-ad”. Should I change (if I ever get the brocho)?
I believe you're right that, in Biblical Hebrew, binyan cannot be construct with ade ad:
But b'rachos are generally in rabbinic, not Biblical, Hebrew (when they're not paraphrasing Tanach), and rabbinic Hebrew may have different rules about ade ad: I don't know.
You ask what you should do if you're saying this b'racha. For practical guidance, one should always follow his rabbi's ruling, irrespective of what one reads on this site.