First, kudos to you for wanting to find an effective solution instead of just caving in to either your daughter or your husband.
First, I am sure that you realize that your anger, and that of your DH, is not helping the situation any at all. Can you find a way to deal with this aspect, separate and apart from handling your daughter? Can you use the negative impact this is having on her to convince your husband that you guys need to seek counseling or some other help? I bet a cooling off on your parts would make a big difference in her behaviour.
Next, can you point out to your DH that hitting her isn't going to teach her not to hit? Seems pretty intuitive to me that hitting a child while saying "no hitting" just doesn't compute. She will only learn that hitting is exactly the way to get others to do what you want.
Maybe those first actions will buy you some time. Because, unfortunately, there are no immediate quick answers here and you all need to realize that, especially your husband. But maybe if you can come up with something where you can at least show progress, that might help?
It sounds like she is a very angry little girl. Do you have the resources for professional help to deal with the anger? I suspect not, but if you do, then I would probably explore that next. Also, you might want to explore a medical assessment and/or diet/allergy sorts of changes while also addressing the behaviour directly.
OK, so now you need a plan of action, one that both you and your husband can agree on and one that you can both implement the same way every single time she is out of control. My first thought is, does she go to school? If so, does she have these sorts of outburst and what do they do? Does it work? Maybe you can adapt that?
Have you thought about a combination of timeouts and rewards for good behaviour? Before, everyone shouts me out on the time-out bit, here is my thinking about why this might be a workable compromise:
* A more gentl approach has been tried and hasn't worked.
* There is a time pressure, in that the husband isn't going to wait for her to grow out of the phase without it getting uglier.
* The husband probably has a typically male need to "do something" and this is about as mild a something as I can think of. WHile it might not be ideal, it might stave off a worse alternative.
* Seems like she needs to learn control and this might help her actually do that.
* Other people are getting hurt in these outbursts and a timeout situation would prevent that.
* It is a sensible consequence in that if you are raging and hitting people, no one wants you around.
* It is an easy thing to do consistantly across people and it can be done every time it is needed and it can be workable with a baby that needs to be protected too.
The big disadvantage I see is that, at first, it will get worse before it gets better. Yes, she is going to scream and kick the wall and whatever. And you are going to have to deal with a frightened baby during these outbursts. But I think if you hang in there, you will see a drastic change relatively quickly. At the same time, I would also try some sort of systematic reward for handling her temper in a good way, be that tickets or extra outings with mommy or whatever. Extra time/attention is probably the most sensible because it is the opposite of being removed from a bad situation, e.g. "If you are nice, people want to spend time with you"
Again, I realize that this might not be the most popular response on a GD discussion, but I'm trying to come up with something that takes into account the reality of the situation, not a theoretical or ideal options.