His auto reflect will handle everything harmful that the nuclear blast will do. He does not even have to do anything or react to anything. Then he can simply escape by flying up (I mean seriously, where else would you fly after a nuke..?) afterwards. He does not even have to filter the air really because he can just hold his breath for like 10 seconds. Acceleration or deceleration does nothing to Accelerator. He mentioned in Index that he can negate Newton's third law, converting the direction of the opposite force to be directed, amplified/weakened, any way he wants.

When he saved Last Order, the entire point was that he did not have any leeway to do anything else except save her. The complexity of the operation needed to save her was just that high. It has nothing to do with his ability to protect himself without any distraction.

He is only a vegetable if the electrode is off. If it is on, he is still as strong as before. He is still the number 1 level 5 even while walking around with a cane after all.

The manipulation of vectors is simply an overpowered ability.