The ONLY reason for a husband to ever hit his wife is if he is in immediate danger from her and having to defend himself-- for instance, if she is trying to hit him with a frying pan or a baseball bat--and that is the only thing he can do to stop himself from being really hurt. (A slap on the face, while wrong, does NOT produce immediate danger!) The same goes for a husband grabbing his wife and trying to throw her out of the house--there is never a reason to do so, except in cases where he is in immediate danger.
If what you have told us here is accurate, then this is a very scary situation. Violence, especially domestic violence, almost ALWAYS escalates. Once certain boundaries, such as hitting, are crossed, they are that much easier to cross again. If your husband has begun to exhibit this behavior, for the sake of both yourself and your children, you need to protect yourself. You definitely need to get help from someone in your area-- you can call the Domestic Violence hotline that HisGirl post earlier and they will refer you to great resources, many of which are free. What you have described here is a man who has already been verbally/emotionally abusive and has now escalated to physical violence as well.
You may not be aware, but if there is domestic violence in the home-- and this definitely is domestic violence, your local Dept of Children and Families can step in and remove your children from your home and place them in state custody in order to protect the children. As the manager of a children's home, I see this every day. It's not just your safety/well-being but also that of your children that must be considered here.
The vast majority of women who are the victims of domestic violence 1) blame themselves (as you are doing) and 2) think "he'll never do it again". Both of these are wrong! It's not your fault that he hit you. He made a choice to hit you. He made a choice to grab you and to try to throw you out of the house. Yes, I know you slapped him, which was wrong, but that still does not give him license to do what he did. And if he did this once, it's just a matter of time before he does so again.
The majority of time, if a man begins to hit his wife, he will move on to begin hitting the children as well. And even if he never lays a hand on them, they witness his abuse of you which creates psychological damage even deeper than any bruises from actually being hit.
I'm sure you love your husband-- but it is imperative that you protect yourself and your children. Choose your children over him. If you act now, it's possible the marriage can be salvaged if you both are willing to go to counseling, etc. However, if you don't act things will almost certainly get worse.
GET HELP NOW!!!
If you need referrals for your aread, you can pm me and I will be happy to help you find resources for your area.