A hard fact of life: You can’t change your spouse.
An empowering fact of life: You can change yourself.
Given this, focusing your her problems when faced with a divorce is giving her all the power, and hoping she will, for some reason, change her mind. Why would anyone do that? Yet, many men (and women) do exactly that when faced with a divorce – they put all the blame on their spouse and do nothing more than yell or whine about what their spouse has done wrong, what their spouse should change, and how others should be correcting their spouse.
A better approach is to realise you are not perfect and the problems in the marriage are not 100% the fault of your spouse. While this may not feel as comfortable and self-righteous as blaming her for everything, it does mean you actually have power in the situation. You can make changes that will make the marriage as a whole better, and that just might cause your wife to be willing to look at some of the things she needs to change.
If she has indicated she wants a divorce, she is telling you she is done. Regardless of why she is done, or if she “has a right” to be done, she is done. Waiting for her to change is fruitless. However, if you make changes, you modify the situation, which might cause her to rethink; to risk looking at the relationship again. If you lead, she may follow; if you don’t lead, there is nothing to follow. If you change, she might; if you don’t change, don’t expect her to change.
So, be brutal with yourself. Find all the places where you have been a less than perfect husband and then try to figure out which of those are the biggest problems. Don’t work on the easy ones, work on the ones that are most likely to be factors in her decision to seek a divorce. Change some of her reasons for wanting out and she might consider staying
If you make changes, and you see she is aware (maybe begrudgingly) you are changing, then and only then, it’s time to suggest seeking some help as a couple. Having shown her you are willing and able to change, you can ask her to work with you on changes. First you earn the right to ask her to work with you, then you ask. If you’ve made real changes and she still won’t talk, that would be the time to bring someone in on your side to gently pressure her to work on the marriage.
Please realise this is not going to be a quick process. It’s taken you years to get to this point, and it’s going to take time to untangle the various issues, and more time to deal with them. If you press for a fast resolution, you will be pushing her towards divorce. Accept it is going to take time, and commit yourself to the process.