ms ladybug SQUISHED!

[Dom R]

. But, he thinks I'm using our marriage as an excuse not to move. It's not an excuse...it's a reason.

ladybug.. i think that you really do not understand what your husband thinks right now.
Making assumptions about "he thinks...", are probably incorrect assumptions.
They're not particularly useful, anyway. How about letting go of assumptions of what you cannot "know" for sure, and focusing on what you DO know for sure.
Focus instead on his email to you?

And I know that you offered to go to counseling in your letter. So you have to wait for him to come back around to the conclusion that if he wants to get out of this repetitive argument, then he needs to go [to counselling].

Sara: Her husband has already chosen a way out of "this repetitive argument". He has chosen "Divorce". And ya know what? it will work for him.
From what he has observed of his wife, he prefers divorce, to living in a marriage like they have had so far. Particularly given that the expectation currently, is "no change". Told directly to him by his wife, in no uncertain terms, and backed by years of experience of it.

If ladybug wants a different conclusion to things between them, it is now on her shoulders, to show her husband, that she CAN, and WILL change. To show him that being married to her, will no longer be like the past. Otherwise, he will divorce her.

I hear retrouville is great for "communication". The thing about communication, though, is that it is only a means to an end. It is usually supposed to culminate in action.
A large, significant chunk of communication has already happened. Further "communication" will have little results. It is now time for action.
(with the slight adjustment, that "making a commitment", can be considered "an action" also)