Yeah he's 100% toxic lol
Not like... crazy evil but definitely toxic
tho I do like how his growth is already being portrayed in the story. I'd say he's toned it down to be like... 98% toxic now. I agree with you, but think the author is not only attached to his backstory, but is aware of who he'll be after he's fully developed and reflected, which is why they're denying his toxicity
But yeah, I do appreciate the author reflecting on the way the whole sex thing played out. They didn't outright say it, but Su-ah is a rapist. And that definitely seems like a writing mistake based on who the author wants him to be.

this is the first time I've seen an author apologize for how a sex scene was presented. even though they don't yet think Su-ah is toxic (he is), I believe it's because they are emotionally attached to Su-ah and his full backstory