You obviously know it's affecting the children and it will get worse if you don't stop.
In the example you gave, you caused the argument. You should have asked your DD to go and ask daddy, because you're busy cooking, or nicely, without swearing asked your DH if he could do it /help.
Your children will begin to see swearing as everyday vocabulary.
I know you wish he could have stepped in automatically without being asked, but men (some) get engrossed in whatever their doing and need it spelt out.
By shouting and snapping as you did, your DD will see it as her fault the argument started. The behaviour will start making them behave in a similar manner and snap at each other if they are to getting what they want.
You and your DH, need to promise (each other) not to argue in front of the children.... It's scary for a child as you know from personal experience.
I know that feeling too. It's horrible.
Perhaps some individual counselling would help you as well. Google 'low cost counselling services' in your area and you should get a list of places that have reduced fees.