I vote for marital/family counseling NOW. The poster & her husband need to figure out how to configure the family that they've created so that they can all tolerate and enjoy each other, and it's possible the new husband has no idea how to handle ... well, whatever situations are presented by the new set of kids.

The guy COULD be abusive, or maybe he's just not able to work within the system that the oritinal poster and her children had going. Maybe he needs something else. Some one on one time with his stepkids so he can feel bonded with them??? Or less time with them and more with his own? Or a schedule where all kids were out of the house at the same time (visiting other parents, maybe) every once in a while to have alone time with the parents?

Or maybe it can't be worked out.

But without talking to him and finding out what's up, it's not going to work out. Counseling would be the most likely way for the two parents/step-parents/co-parents to figure out how to organize their new roles and the kids' new roles in the newly formed family. If it can be done. If you love each other enough, it's worth the work and compromises that you'll BOTH need to do to make this happen (assuming he does not have a serious emotional problem that makes him abusive by nature, in which case you will find that out through counseling and be completely certain with your decision to leave in those circumstances.)

Good luck.