My husband frequently yells at our two preschool aged daughters. Sometimes I can't tell if he is disciplining the dog or the children. I have discussed this with him many times to no avail. Parenting classes and counseling are not an option at this time as I work two jobs and he is currently in class all day and watches the children at night while I work. There just aren't enough hours in a day to even get enough sleep. Money is also an issue. My husband has been unemployed since June.
Sounds like you both have too much "on your plate" to relate to each other or your kids in a relaxed manner. My guess is that his not working for this long a time has created considerable self-esteem problems with him and tension between the two of you and in the household. When do you get to enjoy each other as a couple and as a family? That has to be a priority. I understand the economic issues here but you folks need to be more creative in giving yourselves a chance to feel like you're more than two strangers in the night.
In terms of his treatment of your little girls, I'm sure his personal frustrations come out in his expressions of anger at them. Would he be OK with occasionally spending some special time with them alone, on the weekend, doing something inexpensive but fun. He could spend time with just one child and you could do something with the other. This would give him (and you) a chance to relate to your little ones in a relaxed manner, get to know them better one on one.
If you can afford one parenting book, buy The Parent's Handbook by Dinkmeyer and McKay; it's a superb, nuts and bolts guide with a compassionate view towards the struggles of parenting. Good luck balancing your work and family. Sometimes it's wise to step back from the rat race and rearrange your priorities.