My Journey on Lincoln's Assassination

[AussieMick]

Nup, sorry. I dont consider the statements of either Conger (reputable or not) nor Corbett as anything substantial.
(in modern times, when a presumed offender has been shot by police with no independent witnesses the statements of law enforcement members are often regarded with considerable cynicism).

The bullet 'transited the body at a downward angle of 25 degrees above horizontal' ? Is it not possible that the person was bent over or stumbling or (likely to my mind) crawling?

Using an Occams Razor approach ... the most likely scenario is that the person was desperate to get out of a burning, choking, barn. Surrendering? call it that if you wish, I'd say he just wanted "out!" And he may have dropped the crutch or thrown it away (its irrelevant, I think) ... similarly weapons. So he's stumbling around towards the door and (if the bullet did transit downwards) he was shot as he was crawling (due to gammy leg and to avoid the hot smoke which drifts upwards).

As to why he didnt surrender earlier , I gave 4 (I think) possibilities ending with 'We dont know' (and you might like to consider using that one).