My husband and I have been married for 5 years. This is his 3rd marriage and my 2nd. We have 2 children together, and each have 2 more from our other marriages (6 total). Over the course of our marriage he has been verbally abusive to me. I have threatened to leave so many times. He has also been hard on my two daughters from my first marriage. I finally left, and we are now separated. He is seeing a counselor as I am also (a separate one). He is acting like he loves me and wants me back. He buys me flowers and compliments me, but when it comes to my kids he is still resistant. I think he just doesn't know how to act towards them. He wants to get back together, but I'm afraid he'll treat the kids the same as always. How do I know when and if to let him back?

I would say after you finailly start joint counseling and work out the issues

Yeah it is good that he is not 'too macho' to go for counseling but if you are seeing separate counselors then neither one probably has the full story. Even if you go separate you need to have a mutual 'go between' that can see the full picture.
It is hard to say if you should get back together or when but make sure he has learned to react to things different rather than just knowing the right words to win you back or he will very likely go back to taking you for granted. He probably doesn't know how to bond with your kids and it may be a permanent problem but he needs to at least learn to have a decent relationship toward them. Some fathers just don't know how to relate to daughters and them not being his own make it harder.

Thanks for your advice. BTW we have had joint counseling in the past, but it didn't work out too well. He is an attorney and is very articulate. I get very intimidated and end up so frustrated and misunderstood. Also, I think I'm at the point where I am soooo sick of the crap he has pulled that I'm not willing to sit and listen to his complaints about me. I need to hear some accountability from him first, and to know that his abusiveness will end.

It takes two to tango. You either get on or you don't. If you don't and he is abusive to you and your girls it would be a huge mistake to go back to him. How do your children feel towards him? It might be worth listening to them.