Kudos on getting the PC going, hugshelp!
FS, it may hurt to hear this, but I think you may do well with some space from your son and FDIL right now. I know you love him, but, IMO, you shouldn't be around people who steal from you/whom you can't trust.
Beyond that, I think it's normal, ladies, for parent/AC relationships to change somewhat after the AC gets married or develops a serious relationship. I'm no stranger to that. DD seemed to have less time for long conversations w/ me (yes, we had them, too) after she got married and even less time after she had kids. Not only was she busier, but I imagine any long conversations were now w/ SIL, focused on their needs, hopes, concerns, etc. instead of w/ me. No doubt, it can be a little sad for us parents, we miss the closeness, etc. But I think most of us are also happy for our AC that they have found love and started a family of their own, etc.
But when a parent/AC relationship changes to the point of NC or even VLC (very low contact), as has happened to some of you here, no doubt, that is very sad. My heart goes out to all of you once again.