Merlotmary,( great name), I like your post and I am glad you are back.
I relate to things you've said in earlier posts.The few step mums I have spoken to in RL say the same sort of honest accounts of struggles. I have them too. This is completely in the realms of normal.
Now this development at school might just be a turning point! Fantastic that outside influences will steer things in a direction you agree will make life all round more harmonious. If it helps, it will help everyone be happier.
I can see that in your post you are decent and kind. I wholly disagree with people who advise you to leave your husband. Ridiculous. He is your love and you have committed to making a new shape family together. It's just hard to form and shape it. I doubt you thought it would be easy but didn't think it would be so hard. You have made a commitment. I can see you want take it work.
Maybe you are a very competent person. Perhaps this has enable your hubby to be more lax. I wonder.
18 months into marriage I was in the same place as you. Feeling like no one could hear me scream (I was too kind and polite to scream out loud, knowing I would do myself an injustice being shouty anyway, and inside I felt demoralised and unable to cope, and felt powerless to settle on a lifestyle I could live with. I felt hard done by and trapped. A bit excluded. Terrified of what future I had in the new family. I felt the small things added up to an impossible living situation. And they did. It had to change).
Give it some time. It does get better. I have been married only 4 years and having hit rock bottom things have come up roses after a very hard grind, and I now absolutely love to bits my (better chosen than first time) husband, my home and my life. My relationship with my steps is much better, in fact almost indiscernible from the conversations and mothering of my own children in simple conversations. The steps give me the impression they want to please me now, surreptitiously looking for praise, asking me how I am. I feel warmer to them again (like I did in the beginning). This is a complete turnaround! It is entirely possible for you.
Some key things happened. Majorly, my relationship with hubby improved, in that our TRUST improved, because i was less judgey of his parenting, which led to more honest communications.
Communication is the key. Trust is the bedrock.
In practical terms, I chose to accept hubby was a loving dad who was soft and hat I couldn't wait for him to miraculously change. I disengaged from step's eating style, but found I would not tolerate not sitting on a "Chairly Squarely" so i would corrext that. If the living room behaviour was bad I stopped deferring to hubby and told the children to play elsewhere myself.
One of my children went though a bad/risky patch and I spoke openly and honestly about my worry (and horror) to my hubby, and he was so supportive. It also meant it wasn't always his children who misbehaved. Mine did too. That helped a lot. The new equation meant that I wasn't lording it as the superior parent.
Hubby and i started popping out for dinner once a week, only 6.30 -8.30, and cuddled more in front of the children, and I accepted that I should plan our outings and holidays rather than resent being trapped, and that being responsible for MY happiness, I should be a little less self sacrificing. I accepted that hubby could love his children to death, and would instinctively spoil them, but I could gently coerce the steps to behave more decently if I coached them firmly and with kindness.
Say NO to running through he kitchen. I wouldn't have got my D H to a table meeting to agree this, he would think it all too new age, but in passing, me saying "That's It, I won't stand for running in the kitchen" and following up with "X, no running!!" "You won't eat pudding with us if you do it again.." That should work. But you have to follow it through. Deny the pudding yourself.
I left a raw steak and an unpeeled potato on a worktop once, for one step, whilst the rest of us ate. There was a flurry of texts to birth mum and my hubby was really upset with me, but after some days I gained respect because I wouldn't be walked over. Why should I cook if disrespected? I had been a bit of a mug, leaving Doting Dad to do all the consequence management of a naughty child, when I knew he'd not action any consequences!
Incidentally, whilst I put in stronger and more positive effort in with the steps, I also gave my birth children more hugs, love (and token gifts) so they didn't feel too anxious at the change of pace with mum in the household. Your boy is 15. You could ask him for advice about getting the young ones to behave.
You CAN get to a happy equilibrium at home merlotmary. It takes a lot of effort and nerves of steel but it is sooo worth it. A proper family home for you and all your children. That's what you want, isn't it, where everyone feels safe and happy. And that means you too! Accept your part in being part of the solution. Take control of your happiness at home. You're not powerless to affect great change. You and hubby together, children who grow together, general behaviour patterns can get better with time.