just wanted to point this out,since i see many people not understanding this:the point of the cuffs is not to threaten sanji's life,it's to threaten the safety of his hands,which sanji considers important because he's a cook.at the very least,his hands would be damaged a bit,which sanji has explicitly stated he doesn't want.it is directly stated by judgeso really don't understand the argument about the fatality of explosions.i mean,no one even expects sanji to die because of the cuffs
the problem is that if we base the damage of those small devices on the amount of damage big warriors of the manga have taken from explosions during the story,that explosion shouldn't even be able to damage his hands..let alone if you take busoshoku haki in the equation,that would make them even sturdier the fact that it has been explicitly said that the tech is the same we already saw at the neck of slaves in sabaody doesn't help either,since they weren't particularly impressive in terms of power yeah they are a plot device and as that we should take them,but don't make much sense in the world of onepiece against a guy like sanji…even usopp back in little garden fought against an explosion man,and still didn't receive any particular long lasting damage
--- Update From New Post Merge ---
@Kurloz:
in the first part is saying that it's sanji that should consider him his father and serve him and do as he said but of course it only works one way for judge, sanji should care for him,but he doesn't care for sanji at all that's why saji during the combat asks if blood parents should even be considered as someone to revere and respect,if they never did anything for their son other than conception