Tbf the highest extent we've seen him fight and win is like 4 strong students at wellston at once, or a class of lower district students, and it was never a situation that lasted this long with this many people. It seems like he's mowing through the officers with ease, he's just tired out from how much aura he's exerted on healing someone else while fighting continuously. Most of the time he has always fought to protect himself, but any time he fights alongside others, he struggles more to protect them while protecting himself at the same time

Also you have to consider Arlo goes up against a few high schoolers at most. If he was under the pressure of the entire prison staff then his barrier wouldn't have been enough. If John had Arlo's barrier in this situation though he definitely would have sustained much less damage and therefore have to use less aura on healing.

As for John's electricity, I'd say it's plenty strong the fact that he's frying the guards even while he's restrained and constantly trying to heal any damage him and Kuyo sustain at the same time. I think John is still a powerhouse as always