This whole process is full of one step forward two steps back issues.
I hit one today, myself.
It's part of it all. We just want as few of them as possible.
Your laying things out weeks ago is not something I cannot comment on because I did the same thing and while it was a setback for me, I learned a lot from it and have since changed my path. I'm not sure I'd be on the trajectory I am now without that so there's that for you to ponder.
I think it's great that you're in tight with MIL but you really have to make things clear about your game plan and how she's hindering it for you. She needs to steer completely clear and NOT step in. Have that talk with her and make it serious. I'm sure you know that though.
If you detach more (easier said than done) it doesn't feel like the bottom drops out of your progress. It just feels like a setback and then you get back up and move on.