DnJ is one of the best posters on here, so it would probably be wise to listen.
You've received two very different approaches from he and I. Ultimately the choice will be yours how to proceed. But either way, they both lead to the same place: a better version of you.
I agree with most of what DnJ presented, except, as you just mentioned, what if she never does file? How long are you willing to live with and support someone that is clearly just using you? I agree that ultimatums rarely work, and what I suggested isn't an ultimatum. It's a definite move forward. To me, as hard as it is, the blatant disrespect she is showing towards you, your children, and the lives you built together is almost unforgivable. But I also understand still wanting to save the M. It [censored].
Married: 15yrs Ages: Me 49, W 44 Kids: S12 BD: around 4/14