1) Stuart left more because the struggle between dog and man. Even he could tell not all was well, and it wasn't just a case of the dog freaking out.
2) No. I will tell you nothing, you'll have to wait.
3) ooh, someone's been doing their research. Yes cats, both big and small, ave what is often described as a barbed penis. The inflammation this causes to the female on removal makes in less likely she will mate with another male quickly, and thus increase the first male's chances of being the one to impregnate her and thus continue his genetic line.
Why do I know this? Oh, the scary internet places I have been in the name of research...