I'm a big believer in the BioZyme/VitaFerm products and they've always worked for us. At this point it wouldn't hurt to try, especially with your jackpot coming up soon. You can either use the paste or the drench, but administer it to your steer as it directs. Hopefully, he'll start to pick back up and if he does, I suggest adding the VitaCharge powder topdress to his feed every day. I keep my picky eaters on it all year long and it definitely helps. I would also keep him on the sure champ, too. That stuff does wonders. Also consider getting some stress tubs to give an extra kick? We've had great success with all their products so I would hope everyone else does too.
What do you feed him out of? If it's a tub that you leave in the pen all day or one that you never wash out, consider rinsing it (do not use soap, unless you rinse it extremely well) and scrubbing any old molasses or dirt out of it. If they smell something or taste something funky in their tub, they won't want to eat.
Does he act hungry when he comes in to eat? Does he pick around at all?
P.S- We used to feed a similar feed to yours I'm thinking, our local co-op had a 12% show flake feed. It is a very dense feed, especially when it's weighed down with molasses. We switched feeds this fall because we were sick of the inconsistency of each batch.