I don't know that the picture-taking is necessarily "creepy" (though you know the guy and we don't). Maybe he figured you were on a mom-daughter outing and he didn't want to intrude.
Your mom has to manage her own relationship with her boyfriend. You can encourage her but you can't fix it for her.
As far as your ex goes, he sounds like a pathological liar, among his other no-doubt sterling qualities. I'd make sure LB knows how to tell if dad doesn't seem "right" and make sure she has a phone to call you if she needs you. Have you had her in counseling or had discussions with her about her dad's drinking?