Level 4 is the Limit Breaker stage, and generally just buffs what a Superhuman already has by taking off some of their pre-existing limitations their powers had whilst nullifying all their human needs. The MC's next evolution will definitely buff both Body and Memory in him, though I've no clue what that means for him, since it's some limits, not all.
A higher energy capacity wouldn't solve this, because that's not actually the issue. Electricity doesn't overcharge the MC's cells per se, but actually forcefully activates his powers in a way that's completely and utterly outside his control.
As much as a detriment electricity is to the MC, it also seems to have massive potential. Mainly because it seems that, for better or worse, electricity is treated exactly the same as Monster Power by the MC's body. It's explicitly a foreign source of power completely separate from his own internal supply, yet acts as a completely valid source to fuel his supernatural body. He clearly seems to have inherited whatever mutation Syla had, so maybe he can learn to direct it like she did. In early fights, residual amounts of electricity was shown to actually aid him by accelerating his wound regeneration.
