How many chapters do we have left again, 3?
I cast my vote on commoner dying because of the injuries.
Alternative better ending in my prediction is he has to amputate those limbs, how many that are needed (two legs seems likely) and will live as a disabled veteran soldier under the care of the slave. It'll fulfill the purpose of life for the slave for sure, but not sure what the commoner himself will think of that result. I mean, he didn't bring upon this to himself. Sure, if slave didn't snap, he'd soon be sent back to the frontline and, more likely than becoming a glorious war hero and getting to live a good life, he's more likely to either die there or end up in the same situation, but still live in his own house and country.