Nina, I take your point but I would seperate the two examples:
ie, yes, you're right about the proportionality of people who do make the kind of choices I offered as examples, but I don't think that takes away from the fact that the choice is there. I am not naive though, and of course I understand that there's still progress to be made - a male nurse still gets raised eyebrows, a female being the main breadwinner while the husband stays home to look after children is still worthy of comment and perhaps some sly digs. But it's going in the right direction.
On your examples, absolutely, I agree that those are huge problems that still exist and that need to be dealt with, but I am not sure that choosing to implement your "choice" re name, career etc (or not) will have a direct impact on things like SMP or pay gaps.
Overall, I'm a big believer in language perpetuating meaning, and therefore instinctively wish that everyone chose to use Ms, married or not. But, even more than that, I believe it's choices that are important, so I respect the choices others make and remind myself that at least they are choices, as opposed to edicts handed down by law or society. In the meantime, I often think of wedding rings as a good example - it wasn't that long ago that few men chose to wear wedding rings and men who didn't want to wear one were considered normal. Now, most women I know insist that their husbands wear a ring if they're going to. So in that case, both the husband and wife are visibly making a public statement re their marital status - but nonetheless it remains a choice.