FM, as other's here say it quite frequenty: our spouses are no longer the same people they used to be they are as-if the aliens abducted them and replaced their souls with some cruel bug-eyed-antenna-people's and sent them back to earth.
Don't let it bother you...let it roll off your back. Better yet, don't check his FB page. The best thing to do is shut them out of your life, don't be inquisitive about their whereabouts, what they're up to etc through friends or directly or via hacking email accounts (speaking from experience). I know it's hard and I too agree with what you wrote earlier about them knowing our core values and how we feel about marriages and parenthood. Right now don't worry about all that. You're a strong thoughtful person with great values and morals and no one can take that away from you.
Me: 35|WAW: 38|D: 6yo | http://tinyurl.com/2dxx7m6 Feb 2006, left, came back in two weeks Aug 2006, left again Apr 2007, filed for divorce Dec 2007, reunited Mar 2010, moved out, filed again