I think if Sark has any interest, it's a 'thrill of the chase' kind of thing. If he actually succeeded, he'd drop her because it wouldn't be fun anymore. But to see him try is the whole fun of it.

And, yes, Vaughn is a total marriage slut. I mean, if you truly love someone, you are not over them and married in two years! Heck, even if you mourn a year, that's only a year for dating and marriage, which is rushing it. A six-month mourning leaves you longer to date and marry, but still...