He has abused you, which puts you in a different position than if he hadn't. I can't see how it's going to make you seem like the crazy stalker ex, except I guess that you were looking at her photos on on FB but with mutual friends and the way timeline works these days it's almost a given that you're going to see something if it's not made "friends-only", which is obviously isn't seeing as you could see it from your profile.
Anyway, even though she probably won't listen, at least you know you've said something. If I was in a relationship with someone who had abused someone else, and I was told that information, while I might not believe it straight out (you know what new relationships are like), it may make me wary of signs, maybe alert me to warnings later on, and maybe it'll stop her going through what you've been through maybe because she sort of knows? Anyway, that probably came out wrong but I don't think you're crazy, and I think it's human nature to want to warn/protect others who are in a vulnerable position, especially one you have been inor can relate to.