Ok so here is my final piece of advice.
Sit down with your dh and have an adult to adult conversation, do it on neutral ground outside of the home, take paper and pen with you to make notes on what you agree, disagree and can compromise on. Take all blame and "I this", "my that", "you this", "you that" out of the conversation, don't harp on about how you got to the point you are at, take it as "this is our current situation and we need to find a way to make it work and be a pleasant and comfortable environment for everyone". Find the middle ground between your differing styles of parenting.
Once you have had this discussion and come up with an agreed way in how to improve things, sit down together with the children and say to them "we've come up with a way to make everyone's lives easier and better, but we need you to be on board with it to make it work, it is all our home and we all need to live in it and feel happy and safe in it" then discuss it with them and come to a compromise and agreement that everyone can sign up to and no-one feels marginalised.
You will, however, have to accept that your step children are the product of their environment and circumstances, they are not you or like you were at that age, and even if they had the same circumstances as you did as a child there is no guarantee they would be like you were at a comparable age, we are all different and can react differently to the same set of circumstances. Stop comparing them with you and your upbringing and finding them wanting, that is your issue, you need to address it and work with the individuals you have not the ones you want them to be or think they should be.
You do still need to look at yourself and your reactions to things and remove the chip on your shoulder regarding your perceived injustice of the situation you are in. Also, your "I, me, my" attitude needs changing, there are four of you, whether you wanted that or not, and the only way for any of you to have any semblance of a happiness is for you to accept that, compromise, and see it as "our situation", "our home".