I experienced the same kind of disappointments with my now XA after years of supporting and sticking with him through years and years of his not staying commited to what he knew would keep him sober.
There is nothing more frustrating than to have so much invested in a partnership with someone who has done everything in their power to keep you emeshed and involved with unending promises and then witness them white knuckling, building up to use and knowingly neglecting their recovery.
In my case I finally accepted that he had the ability, tools and knowledge to be sober for the rest of his life but he didn't want lifelong sobriety and needed alcoholic "vacation relapses". In the past, I or someone would pick up the pieces and put him back on the wall like Humpty Dumpty but I warned him that I had resigned that role permanently.
He didn't heed my warnings and the last relapse was the last relapse... a boundary that I had set and for the first time... kept it!
I am so very happy that I made the decision to let him figure it out on his own and if you choose to do this you will be able to see how self sufficient your partner can really become and how quality of a recovery he builds.
The only recovery that lasts a lifetime is a spiritual recovery and if you feel he is white knucking then he is and that never lasts...
take care of you and your kids and more will be revealed.