The man has no magical aptitude, right? How is it that he can anti-magic other people's spells? My head canon is he is trying to take over the casting of the other person's magic spell. Because he is now the caster his anti-magic curse erases the spells he is trying to cast. It could be...
As we get further into this arc I can only come to the thought that this author has very limited character archetypes and personalities. "Oops all wizards" arc really highlights this issue with all the wizards are nearly the same kind of wizard.
The Panama canal would have been wrecked by the passage of time as it is not just a trench dug between the two oceans. It relies on a lot of moving parts to facilitate travel of boats and would need a lot of staff even if there where still computers and power to run the locks.
That said I am...