Yes end it's misery NOW
The extent of the damage is TOO severe, even if the vet wants to try to get him better and a smart vet would not do this, the chances are very small.
The animal is too young, too small, the damage is extensive, the animal will either die from it's wounds, infection, stress or starvation, because lets face it anyone that had to assist or force feed BP know how stressful it is even for an healthy animal and in this case the stress of assisting or force feeding will likely be FATAL and who will do it?
It's better to end an animal misery now than prolong it's suffering until you can find someone to take him or see him.
That's the harsh reality I know it's not what you want to hear but it's the truth.