Although it's not necessarily impossible, it's not likely that this little guy would have survived recently in the wild with the severe deformities he has. That isn't to say that he wasn't at one time wild before his captivity. Remember, this sort of deformity could also be accompanied by abnormal growth rate, or none at all from the point of capture. In the same way, it can affect color. As such, all we really know is that we have a box turtle of unknown origin, and unknown lineage. To make 100% assertions to either his subspecies or origin is just not reasonable.
Luckily, all North American box turtles have (essentially) the same care required, and his status as a wild or captive turtle doesn't make any difference. His current conditions do. If you don't feel up to the task of rehabbing this guy, PM me about a few people who may be willing to do so. I only suggest this because often such severe deformities mean he'll require very specialized care, often far beyond what most rescues will provide.