It's taking over because your whole life is changing. It's especially hard when it's one partner leaving the other for someone else. It's harder on the one being left behind because it's something they don't want and they are being put in a vulnerable position and it can make them feel like they have no control over anything. Right now though the children need you both because their world is being shattered and they will be affected by this the rest of their lives. You have to try to be a strong Mummy for them. They will thank you later and they will save your sanity.
Yes. You and the children can have a good life together. Remember they were left as well.
If I may ask, what are his claims of divorce?
I don't mean to doubt what he has told you as his claim, but surely you do NOT believe that!?!? There is another reason he's not telling you, trust me on this.