You could try to find this item https://tos.neet.tv/items/103301
It reduces your magic attack by a whole lot, so if you unequip everything else on your character, you might be able to use Chortasmata just fine.
Otherwise you’d have to get someone else to reduce your stats in a field battle, or have them buff the monster so it doesn’t die.
Oracles “Change”-skill could also help to reproduce the monster you’re looking for at a higher level with more HP/defense, but it will take a lot of time to get there.
But yeah, such problems should be adressed at least with the upcoming Re:build-update so people can use the system to utilize their skills (or just remove the type restriction completely)…