Welcome to divorcebusting.com. As you will see in Divorce Remedy ... an ultimatum is the AFTER THE LAST RESORT technique...and while you have READ a lot, it doesn't mean you have necessarily TRIED a lot in a productive manner.
We are here to help you brainstorm some solutions and give you support, you will find some really great advice.
Be patient. Work through it. Begin as if the problem were new and you've had no advice. It will be worth it.
On a side note, a couple of your references have been edited, as in the specific references are known to be contrary to DB advice.