I don't think there is anything wrong with naming your child after a character per se. I wanted to name my daughter Kira after a character in a novel, even though that character was a selfish git. Unfortunately, it's also the name of a killer in a horror movie that is much more over-reaching in society now, so my husband vetoed it. (Boooo!)
However Severus would not be good. As mentioned above, it sounds like "severe-us" which is graphic and unpleasant. Not to mention that its only association is with Harry Potter. It's not like Harry or Ron or even Hermione that could be family names or just names in the popular lexicon.
I say adopt a bird or something and name him that if you want, but choose a less graphic name for any child you might have.