Most of the time it is not what or how much you feed to finish a steer but that in combination with time. Finishing steers quickly can always come back and get you and if someone had a magic deal they would be rich! Next year I would recommend looking at increasing his feed at earlier intervals, right around the 1000lbs mark I would also suggest looking to switch over to a lower protein finishing ration (12-11%) this will come sooner as you increase feeding levels on an earlier timeline.
Right now get him on some gas. Keep protein around 12% and increase fat and pour it to him. At the start you will have to gradually increase the feed but get him eating as much as you can. I would suggest trying to target your final feeding amounts around 30-35 lbs per day.
This is all depending on the calf and I have not seen him, just a thought. Playing with the ration is totally up to you but I would make sure he is eating good and gaining before I started playing. Rations are like opinions, everyone has the right one but to each person (animal) the right fit is always different.
If you need help ask someone, don't be afraid to call up a local sales rep or what you think are experts. Get their opinions, if they can come look that is even better. The final choice is yours but there is a lot of info out there and options.
I hope things work out for you!