Hi Seaweedandsand. You need support here. Seems you planned things with eyes wide open, just like I did. Being Captain Sensible, was our phrase, so we had the best chance possible of surviving the likely pitfalls of joining two houses and step kids.
I want to encourage you and pass on our experience - I think that is what you have asked for. Not a harsh post-mortem on your planning process.
After we started living together we did continue to discuss things well, and also by arguement at the bottom of our garden (!) but also we chose to skirt round things - letting things go, and not continually raking over the same stuff.
We coordinated the ex's parenting time and attempted to have time together with no kids every other fortnight - just for the Sat night til 8am Sunday.
One ex refused to rally to our need at first - why be tied to the other ex? So my advice is to not mention the other ex, but to submit a rolling timetable, long plan, access/visiting arrangement so you can plan some alone time.
Our plan falls down regularly but we don't mind, we are happy to have the children more (usually), but the pattern doesn't change over the long term. This way I can plan things in for the future. The 'other parent' dates are on repeat on our google calendar which DH and I 'share'.
When we first got together the google calendar was so useful.
We also banned some things from occurring in our bedroom so to keep our room a relaxed space. We introduced this because we didn't want to argue in bed (first chance alone and place we could go to debate, and a place I was offended if DH texted his ex).
I also stopped trying to be SO FAIR between all the kids. It was crippling me. I had to detach a little from the steps and give a few more private cuddles to my lot, so they knew I was still their biggest fan and adored them. This has all ironed out now.
I encourage (still) DH to have good interactive time with his lot. DH is a man, and a very paternal, if not even almost "maternal" man. But still, I think I see plaintive need in his and my children, and I am happy to nudge DH to step in.
My man, (in my opinion) thrives on admiration- not in a wierd way - and he got angry with judgement. So, I advise you to see the good in dad's parenting and speak the positives. You probably admit, he tolerates rudeness better than you. I doubt he enjoys it. You should remain smiley, and non judgemental and try to be part of the solution in situations and try not to be judgey pants. (Not easy). And don't forget to praise his strengths.
Set some boundaries. It's fine to go out when the steps are over. Make a decision about what you will and won't do. Detach a little, and try not to be resentful. I chose to let table manners in the steps go, as not being my responsibility. Initially it offended me so much. I decided to not comment, but to still comment on my own. Over time (years, I am sorry to say) they have normalised.
If your step children are older than your two, it is fair to say that you might become a little horrified about some of your children's behaviours as they reach the age your steps are now.
I don't think Swing has step children and I have often thought my blended family would be easier to manage if there were only one set of kids, without divided loyalties and huge sensitivities. I could have dominated the household, and made the rules for all of the children.
Melding two families is inordinately hard and living together and sharing space is not easy. It's not ideal either, and there are kinks in the road ahead and, for me, I wonder how many of the successes and difficulties have come about because of divorce and (in my case) remarriage.
My experience is clear though, that on balance the children benefit hugely from step parents and step siblings, and I truly love my step children in a far warmer way than the way I had to occasionally fake it in the early years. At your stage I was sometimes close to walking away, it seemed too high a mountain to climb, even though I had wanted to blend us, and knew it would be hard. So I know how you feel.
You can do this. If your step children are small enough, I recommend some of the things I did: putting a tent in the garden for them so they played outside and ate outside!
Using two cars to go out for the day all 6 of you.
Planning in advance to be away sometimes.
Doing small acts of kindness to warm the children's hearts to you. E.g. Helping with a school fancy dress, or buying water balloons for them.
Take time to have their grandparents and other replies over.
Praising the kids and DP when it is appropriate.
Never trying to replace their mum but doing mummy things for them - that warms your DH heart too.
I love cooking - so I cook alone for relaxation and o make what I think the kids will really like.
We take holidays together and also they go with their other parent.
Put music on in the house to make things cheerful.
Have pizza nights (then go off for a bath).
Show affection for each other as a couple even when the children are onlooking.
And the biggest one - have a calendar!!
Kindest warmest wishes.