I have never come across any specific indication that Ruby saw the footage, and I've been at this, on and off, since the year xxxx (redacted by RC). It was, of course, frequently played on TV, so I would guess that he must have encountered it, unless the prison authorities kept it away from him. If he did see it, he might have realized the truth. Perhaps that's why he switched from telling Earl Warren that Lyndon Johnson wanted to pursue the truth (unless he was being ironic) to fingering Johnson ('the man who is in office today') for the crime after one of his later court hearings.
As for Dorothy Kilgallen, I suspect that in the early 60s people were not so clued up about psychology as they are today, but someone as sharp as Dorothy Kilgallen might have guessed the truth after hearing Ruby say that the incident was a 'blur', etc. She might have known before he did. She probably concluded that 'this guy is a bruiser but not a killer'.
RC: It registered with me that Ruby pointed out that he didn't use any bad words when chastising Oswald, that he didn't call him an SOB or anything like that. What a thing to worry about in that context. Was that the good Jewish boy in him? Now, don't anybody take that as anti-Semitic. I mean it respectfully. I'm saying he was a person of faith, which I certainly am not. He was a devout Jew. We know that he went to the synagogue that Saturday. We know that he was close with his rabbi. And we know he had a kippah on him when he was arrested. Isn't murder vilified in the Jewish religion? Thou Shalt Not Kill. It's in the Old Testament. Ruby? A killer? I don't think so. Make that: Not a chance.