The armor is dumb yeah but at least in this case it's based on a video game world so it makes a bit more sense.
As for the summoning, pretty sure they screwed him over on purpose. The invocation magic and counter-invocation magic should have the same basic requirements since the concept is pretty much the same, it's just sending someone to a different dimension vs. pulling them from a different dimension. The fact that one specifically required the Princess and a full moon but the one to send him home could be done when ever and by a random court mage (it didn't even say he was the highest ranking court mage, just a court mage) seems suspicious. With them putting him in a cell over night and him ending up in a random place instead of home, it makes me think they were just getting rid of a potential problem (unknown power/personality) but not quite ruthless enough to just kill him.
The only thing I don't get is the random "this is what happens to the lost people of our land" blurb the court mage said during the counter-invocation. It seems odd that it's the only translated part of that scene but maybe something got lost in translation or they'll elaborate on it later.