OP this is such a tough one. As an alcoholic in recovery myself, I was ready to type a response saying to leave him, he can only get better when he wants to help himself etc.
Now I have seen your message that he's going to attend AA - this could be what pulls him into sobriety. It might not be. There may well be relapses. He may decide not to engage.
AA is what stopped me drinking and I have now been completely sober for over 3 years. Before AA, I'd tried every single method I could do myself to stop drinking and none of it worked. Alcohol addiction has such a powerful grip over someone that it's often impossible to stop drinking without outside intervention, however it's also impossible to convince an alcoholic to seek help and engage with that intervention unless they genuinely want to get help themselves.
To this day, I don't know how AA managed to help me. I went from someone who was drinking a bottle of wine and a small bottle of vodka every night, if not more, to just never drinking again. I had to hit rock bottom before I sought help, but AA changed my life and it has the potential to change your DP's too.
If, however, he is simply getting in touch with AA to create the illusion he's working on his addiction while still drinking, it won't help him at all. If he's just trying to placate you because he's, yet again, been caught lying to you, it won't have much of an impact.
AA also isn't like therapy. You can't have 5, 10 or 15 sessions and then be done and walk away "cured". In almost all alcoholics who engage with AA, AA is for life. Many of the members I attend AA with haven't touched a drop of alcohol for decades but they keep coming back, because that's how AA works.
Addiction can only excuse so much - he is still lying to you and deceiving you and there's only so much of this that one person can tolerate before it really begins to break them. Don't let yourself be worn down mentally due to his behaviour that he may not have any intention of changing.
Many addicts in the grips of addiction often can't see the damage they are causing to their loved ones and when they can, it doesn't register in the same way. It's as if it's just an obstacle to get past in order to get what they want (in this case, alcohol).
It's completely your decision as to whether or not you stay with him, but if you do decide to give him another chance, I'd suggest for your own mental health it may be advisable to separate and live independently while he works on AA.