I also will talk to her this week about keeping my S here with me. I think I can provide him a better environment overall. She and MIL are both bipolar. My W is staying with FIL and he does have the 'Flavor of the week' going on sometimes because he's been singled forever. MIL's house is really small.
Have you seen a lawyer yet about your parental rights?
She moved your son across the state line and is raising him in an environment that you think is not appropriate. If you really believe that your boy is better off with you, then what she wants shouldn't matter. Yes, have the conversation with her and try to be as friendly as possible, but have a legal plan in place just in case she goes crazy.
I'm gonna keep nagging you about this...boys need their daddy just as much as then need their mommy. If mommy is crazy, boys need daddy even more.