What do you think of this ending?

I think that would have been an extremely memorable and shattering ending. Kind of bittersweet! I would have been fine with that ending but I think the innocence of the kid and how his father was able to take such a miserable situation and make it bearable (and livable) for his son was so heartbreaking in the best kind of way.

I think the original is better, because the voice over suggests that the kid realized what his father had done at an older age, which means he was able to fully understand and appreciate what he did during such a horrible time

Would be nice if you would've added the name of the one who came up with this idea for a better ending: the philosopher Slavoj Zizek.

And yes, Zizek's ending indeed would've been better.

but then you'd have to change everything

like the tank he wins at the end