Definately a cory, I have my money on C. Trillineatus, it might be a C. Julii. But the Julii's generally have clearly defined spots (versus the line/splotches on yours) and a less defined lateral line.
As to the temperatue, I think he and some new buddies ought to be fine if you acclimate them... I've never kept them with discus, but I've heard of others doing it with no trouble. They're peaceful and like to go in schools, so I'd find him some more friends. They will school across species, especially similar looking species, so keep that in mind if you cant' find any more exactly like him =)