Ok well your reaction wasn't great but it's possible to address that.
Apologise and assure him you believe him - trust me when I say that not being believed is the worst! Most of us doubt our memories and experiences of such abuse not least because many abusers gaslight their victims to introduce such doubt.
Alcohol does not make someone an abuser, it lowers inhibitions but the thoughts/intent are still there.
Unfortunately I think you do need to give serious consideration to the possibility she may have abused your kids and you need to seek advice on how best to check this and if she did how to support them.
Even if they were never alone with her it's still possible.
Don't push on him giving more info or on going to counselling. It doesn't always help and people have to be ready to engage with it for it to be most effective and not harmful.
But you can access counselling if you think it will help you.
Bear in mind he may genuinely, literally have forgotten. Denial is bandied about but there's a clinical definition where people literally lock away memories of things they found too traumatic to remember, it's self preservation, but when the brain stops doing this it can lead to several issues so keep an eye on him and his MH generally.
Overdoing the alcohol wouldn't be advised at this time so maybe discourage him from that?
My ex was very reluctant to initiate any intimacy in the immediate aftermath of my disclosing to him, but eventually he felt more comfortable again. He never pushed, but listened when I needed him too. He didn't judge my still having a relationship with my father, but he then understood why I wouldn't leave dd alone with him, or even my mother (who still doesn't believe me) hell I didn't even like him holding her! But when I reached a point where I decided to go Nc with dad he did admit it was a relief and he believed it was the right thing to do. Unfortunately I was later pressured into getting back in contact after ex and I split and that caused some heated discussions as ex was naturally concerned re dd but I assured him dd would not only never be left alone with him she'd never even be left alone with my mother and wouldn't even be within arms reach of my father.
Dd is now essentially Nc with my father, her choice. Vlc with my mother and never at my parents home.
It's so very complicated when your abuser is someone so closely related. Not least because nobody is all bad, I have very happy memories of our relationship before the abuse happened and it's incredibly hard to divorce that man from the one that became abusive.
Patience is the key I think. Patience and kindness.