Yes, I think 4-5 intelligence would be enough for such a passage. But I think it's not right to be "great at math and spells" with intelligence 4. The whole fun of this walkthrough is that you are an idiot, and everyone perceives you as an idiot with a dead brain. Even the goblin Sazza looks as a more wiser and smarter.
Well no, my suggestion was that you could take the "idiot" trait without lowering your INT because being an idiot isn't about merely not knowing things. It is about making incredibly dumb decisions, not paying attention to others, and misinterpreting things. All of which can reasonably be done with 18 INT. Gale has 16 INT but he still decided messing with ancient forbidden magic was a good idea.
If you wanted to be a complete imbecile who is also bad at math and magic you'd just take 8 INT plus the idiot trait. But having high INT shouldn't stop you from being a moron. I've known lots of really, really stupid but well educated people in my life.
