Violent kids

What would you do in this situation, my husband has an 8 year old from a ine night stand years ago, and I completely encouraged the relationship when we got together, since I brought two little boys of my own into our marriage. There has been on going issues with his sons lying (not tiny lies but very severe CPS got involved lies), still encouraged my husband to try and work through it, although he wants to give up since its causing alot of issues outside of our marriage. Aside from that he has been increasingly violent, I've known him since he was 4, and he has always been violent, but it's getting bad. I caught him trying to stab my 4 year old at the dinner table with a steak knife. ( he is allowed to have a said knife to cut his food and I was present, I had just turned around to get my youngest his fork). I'm at the point where I dont know what to do, and have a very big safety concern for my own children. He is in counseling, and has been for awhile, but nothing we try changes his behavior or his lying.

Added: I will add removing my children from the home for the 4-7 days he is here will not work, as those are the only days my husband has off, so I dont want to miss out on seeing my own husband, and I dont want my two to miss out on spending time with their step dad. That and know where to take them for 4-7 days at a time.