Mike

That gun plain does not fit him.

That is not a slur on him at all, but it is the reason that in the grand old days guns were tailored for the individual. That most of us cannot now afford the bespoke service results in situations like this.
He can learn to shoot this gun, but a better solution than expending the money necessary on ammunition would be to have somebody alter the trigger plate and guard to bring things properly within his hand span. 1/2" or so would make al the difference.

I have relitivly small hands and they are a little stiff from work, so I had to cut really rough checkering on the underside of the grip of my double to get a good purchase, as altering the circumference was not a posibility. This was a poor, but effective solution. Before that I bruised the middle finger to the bone.
I hope that he can sort something out, but I would not take that gun against DG in this situation.

Regards