Gosh, what a handsom boy! You stated that he has white ears, but they look red to my eye.
Cream Legabrs are so rare I would not think of that for the mix, plus they have a crest which yours does not.
Couple of clues to help zero in on the mix
White legs: there are a few breeds that come to mind-Faverolles and Dorkings (but they have 5 toes and he has 4 so unlikely), and 4 toed breeds Sussex, Orphingtons, Marans, Old English Game
-there may be more that I am not remembering off the top of my head. The white legs are a dominant trait so at least one of his parents have to have white legs.
Barring: Barred Rocks, Dominiques, Cuckoo Marans, Delaware (faint), Crele color variations (I think Orps may have a Crele variety)
Straight comb (it doesn't look hybridized with another type)- Dominiques have a rose comb so I think this rules that breed out.
Since he's a mix, you really can't rule out a lot of breeds being in his background. I had a rooster with what I called a cream columbian pattern where his hackles were a lemon color and he was a mix of Brahma and a red sexlink so the yellow golden color from your roo's hackles don't have to be from a Lemon Orp it could be his color mix. My mixed roo bred a Wheaten and his resulting boy has much more brown/red feathers on his shoulders than the original so there may be Wheaten on your mix. My point being he could have more than 2 breeds in his background.
My best guess is a Cuckoo Marans Hen mixed with another single combed 4 toed breed that isn't dominant white (ie not Leghorn). Since he was sold to you as an EE, it could be that the Roo was an EE and he was a mix so the beard and pea comb as been diluted out enough in him that your boy didn't get any of those genes. Perhaps the breeder was working on Olive Eggers breeding EE roos with dark egg-laying hens like Barnvelders and Marans.