Gee that's a hard one. When abusers give the excuse that they're acting under intolerable stress, the test is to see if they take it out on (say) their boss or friends. If they don't, then to abuse their spouses or children is obviously a choice rather than something they can't control. Maybe you could apply this test to your RAB.
He's working on the meds, and behavioural modification which shows effort, but seems to get lazy or careless when he's at home. You could think about what's acceptable, what's over-the-top and harmful to the kids. Maybe confront him calmly when he acts out? Maybe work on some strategies with him where he will 'time out' rather than poison the atmosphere?
It seems like something you'll need to confront for yours and the children's sake, but it would be better to have a strategy and possibly some training on how to handle situations without escalating, because you'll need to stay in control. It might pay to consult a counsellor about becoming more assertive.
You're focusing on what's reasonable for him, in the sense of whether it's the mental illness and therefore not his fault. If the children and you are suffering, walking on eggshells and unable to relax, it might be more logical to stop thinking about the cause and focus on the effect. In other words, getting them out of there.