It's a simple decision do you want a divorce? Yes then file. No then hold tight. In 5 years if your M works out will it matter that your friends and family thought you were foolish right now. In 5 years if your M doesn't work out will you be happier knowing that you saved a bit of money or happier knowing you tried everything you could?
As a former WAW I can say things were going wrong long before the running club you just didn't know. She was probably unhappy which is why she got into running then the other divorced women gave her the validation that she too could separate. No they didn't encourage but if you're thinking of leaving even a little then you look for validation and ignore anyone giving you caution.
Decide what you want to do. Do you want to be married to her or not. Then you can make the next decision.
Detatching is going to be key. But decide if you want to make this work first
