I hear and see you. You're clearly a caring a loving person. You've said nothing that was nasty regarding your step son. Jesus I use worse for my own at times! Main thing i got from my upset i ever worried and got scared about that, was my HV telling me its okay.
Asked me the simple question of if I loved them. Ofc I do. Including my stepkids. But sometimes, its okay to think this isn't alright. This is impacting one kid out of the group. Be it mine, or dhs.
Your dh is being unfair on you to ignore the added stress of a newborn into the mix and the hormones and lack of sleep that go with that. Youre both being unfair on each other for seeing each child on either side as one needing protecting.
Kids row. They are sods! And some carry certain behaviour traits that need sorting. Dh sounds like he needs to teach his kid to know who they can and cannot banter with. And how far they can go depending on who they are dealing with. You do also need to teach yours if you're going to give it, you can't be hurt when its given back.
That isn't a kid is at fault moment. Thats teaching them skills for life. No one wants an adult constantly ribbing them when they don't like it. Neither do people want someone who will give it out but kick off when its done back.
All that said, it is so clear to read how down you are. And its so easy to catastrophise when you are in that place. Add a tiny baby in the mix and its no wonder you're pooped!
Also and I mean this kindly - I speak from experience. Bht your life experiences doesn't mean your son will have the same. And sometimes over protecting can cause more harm than good. A scary road to navigate. I know. But you're doing him a disservice by overprotecting from what is general siblings squabbles. As you said yourself, they get on as a whole.
In time he will find this with friends. He needs to learn to instead to find his voice. And ofc come to you when needed. But also - if he is starting something he then can't moan when the same is given back. Unless of course it crosses a line.
As dh son needs to learn its not okay to push someone who doesn't enjoy that back and forth.
It all sounds like two parents lovinf their kids and forgetting the general dynamics between kids. So they are blinded by "us vs them" it isn't. Its kids being sods. Which can be resolved between you both.
That said the threats aren't okay. You should be allowed to speak your mind within reason without being told you'll be left unless you put up with it.
That is abuse to keep you in line. And that may not be meant on dh part, but isn't okay regardless.
For a happy family unit to work, you both need to be accepting of one sides kids downfall and work together to make it work. If possible.
And it should 100% be taken into account their individual needs too.
Dsc sees someone living with their dad. Hard. Ds sees someone coming into the home and changing the dynamics while both sets are dealing with a new siblings and the worry there.
Both are acting out. Both likely feel a bit lost. But considering you're own needs and history, dh needs to step up. You also need to stop comparing everything to your history. And I mean that kindly.
If anything it all screams a normal sibling relationship! My two are polar opposites so get along... until they don't. One is rough and ready. The other is calm and sneaky!
at times I've sat wondering if it was my sc would i feel so "needs to be dealt with but is normal" . And sometimes, that strong love for our own is harder to move past. Rather than when its just your own.
But we are the adults, and we need to do exactly that. But your dh should also remember your sons extensive history and be aware of how impacting that is on him.