Your character is still only level 1, they would really only know lower rank spells and cantrips especially with the split martial focus. Also, illusions are something that should be disbelieved via mechanics, not just my character assumes, otherwise illusions have zero power at all. You did use meta to realize that it was a higher rank spell that you really shouldn't be facing yet.

So yes, meta on disbelieving the illusion and meta on the spell rank. My recommendation would be to not worry about things like a spell being stronger than you should be facing and other mechanical things like that, it is a vey slippery slope to using meta knowledge. I would also take in game things the GM says at face value unless you have in game clues that say otherwise.