if your hubby understand the situation but just can not control his emotion/temper. Do you think the Reward Chart system can also apply to him??
put up a chart that he can see it easily can remind him.
Kids need parents (both mum and dad). maybe ask your hubby to play with them 10-15mins a day (read story, play lego etc) to start with. If he can stand for 10-15mins to play with the kids everyday, I guess the relationship between dad n kids will improve a lot. and hopefully gradually, he will enjoy the time being with the kids.