This sounds like a fairly common problem firstly it sounds like your doing a fab job we have three kids two boys (11 & 9) and a little girl who is 7 months old. Both our boys are on the autistic spectrum so tantrums and screaming and shouting have become the norm in our house but like Dominic has said staying calm is a must the more flustered you become the harder it will be to stay in control on the situation. As for muttering under your breath show me a parent who hasn’t it’s a way to release I mean would you really want your daughter to hear something that you don’t mean but say in the heat of the moment. Having two autistic boys we have to work to routine perhaps that could help by trying to take a bit of the unknown out a situation. Hope some of this has helped but remember you are a GOOD dad and that your daughter loves you even when she is not happy