I always feel that Canon!Snape's self control is more tighly wound than My!Snape's. He speaks through clenched teeth a lot and virtually vibrates with suppressed rage. I tend to write him more relaxed. Or rather: I tend to idealise him as more relaxed and possessing a stronger sense of humour. Canon!Snape deals coolly with Umbridge in a situation when he is in control (one of my favourite Snape scenes), but he is pretty angry when she inspects his class. This is basically Canon!Snape to me: He is very smooth and cool when dealing with situations and people who don't affect him on an emotional level, but not with those who do. I think My!Snape has a better self-control when it comes to personal matters, too.

I don't think Sirius actively and strongly disliked Peter, but he didn't value him as a friend. Peter was around, he might be useful, if only as an admirer, and that was fine by him.

Ah, the sex scene! I love unpretty sex, and I am glad it works :-)