I think I know what you're trying to say. You can say, "If I'm not mistaken, he will be foul" or "If I'm not mistaken, he is foul" . I'm assuming when you're using 'foul' to mean 'rude' ??

No, it doesn't make sense.🤔

It's good up to AS I KNEW IT. That part doesn't make sense.

"as I knew it" doesn't make sense to me. Like I don't think that is a phrase that we say. Similar phrases: as I thought "It was just as I thought. My sister had gone to the party without me." I knew it "I knew it then and I know it now. I am bad at math." "So the husband WAS the killer! I knew it!"