Dang it T2, you were my hero! Still are! You have 24 years together, I have 25. I so hoped that she would get some alone time and really see just what she is losing, what she is doing to not just you but the boys and HERSELF. I would wait to file. The last month she wasn't "really" on her own as she knew that it would end after a certain amount of time. That might have put pressure on her and she needs to be truly without a net to understand what she is going to lose. Who knows as we can't understand what they are thinking.
One thing I know from reading your posts is that YOU will be fine. Better than that, you will be great. At least you are with your boys and you will be there with them to help them through all this (and they help you as well!). Take some time before you do anything. Maybe she will feel able to talk and not just leave a note after a bit of time has past. Hear what she has to say, what she wants or thinks needs to happen. I'm praying for you, T2!