For many it is simply too emotional to look your wife in the eye and make demands. Often she sees through your sadness and recognizes that your heart isn't in the demands.
As everyone has stated, you need to put yourself back in the driver's seat. There's only one way to do this and it is to take a solid stand that defines what YOU need. It may be too difficult for you to do this effectively through words.
Write out exactly what you need, your requirements for reconciliation. Begin your list with absolute, 100% no contact. Transparency. Independent counseling. These are non-negotiable. You don't need to make the list exhaustive but it should be clear.
Then, have the divorce paperwork in your hand. Give your list to her and simply tell her that these are your requirements. It is what you expect of her and the list is non-negotiable. If she wants to save the marriage and do the hard work necessary then she needs to agree. If she reads through the list and says, "No," then hand her the divorce paperwork. This only means that things are proceeding toward divorce - but she isn't going to recognize that it can be stopped if necessary.
Then walk away and see what happens. Maybe she takes an hour, or a day, to think it over. Maybe she packs her bags and leaves. Maybe she curls up in a ball and realizes that she's just thrown her marriage in the toilet. Whatever it is that happens - YOU DO NOT COME BACK TO HER! You continue with the 180.... you're not there to console her, make her feel better, be a shoulder to cry on.
It is now on HER. It is HER time to run after you. To beg. To openly offer your transparency. To ask you if her no contact letters are sufficient. It is HER time to commit.
It is time for you to turn the tables and begin showing her that she no longer determines the fate of the marriage. She's either in or she's out.
I know how hard it is. But it is time to man up, grow a pair and stand up for yourself.
You know what? You might be surprised by her reaction.
I wish you luck.