I'm just sorry you are in a situation where your DH and his ex still plan joint parties.. that sounds excrutiatingly painful. lol.

I kind of get your POV.. better the pain of being the nagging reminder than the pain of having to fix everyone else's lack of initiative.  The problem is that the dynamic seems pretty set at this point.. and they would likely land in a pile without you.

No offense, OP - but you do sound like a bit of a control freak.  Control comes from anxiety, so I do understand. But they can't make last minute plans because it ruins your meal plans? And who cares if BM gets SD an atrocious cake? Who cares if they got a permission form, or when they'll come home, or whatever.  That stuff is DH's problem. Don't let it be your headache, let him do any last minute running around.

So I am constantly riding them for details about things. Where are you going? When are you going? When will you be back? Did you tell your father/mother/anyone yet? Did you ask permission from ___? Did your friend give you any details? How much is this going to cost? When is the money due?

Disengage from all this. Hope your finances are separate from your H and be done with feeling you need to control things. These are not even your kids and you seem more invested than your own H. I'd let it all go and let the pieces fall where they may. It's not worth the stress of always having to know the details, costs and what's going on with people who are not considerate or appreciative of your energy & time.

My number one disengagement realization was turning this statement around..."also can’t take the stress of NOBODY ELSE doing it because their lack of planning inevitably becomes my emergency (and/or headache)."

Nonono. 

Their lack of planning does NOT become your emergency. Read my blogs for my disengagement journey. One step at a time. It gets easier with practice!

Separate your finances and let them handle this in the manner that works for them

As far as food is concerned, freeze what you don't need so that it doesn't go bad.  OR tell you husband he's responsible for meals(shopping, prep and clean up)

I'm also a planner, so I get the NEED to know what is going is set and in place.  But not everyone is wired that way.

I am a planner. I like foreshadowing, to know what's gonna happen. It gives me comfort to know what's coming.

DH is not, or maybe I should say he only is in spurts and certain scenarios. Since he is not a planner, he also doesn't know some of the things going on and is also surprised but he handles it since he's not a planner and almost everything seems to be last minute/a day away in his life. I've even had to have the conversation with him about how I'm supposed to know about things (and he's upset I'm not just magically available and willing to do whatever it is) if he doesn't tell me or how I'm supposed to know to ask exactly the right question to get the information that a plan is being made. Am I supposed to go through a litany of topics every day? I told him I can so he'd better be ready for about an hour of questions. He didn't like that scenario, duh. (Neither did I but I was prepared to follow through with that method to show him what it looked like.)

It is HARD, trust me, to disengage and not care. (like painful for those of us who like to know the plan) It took me a looooong time to learn to ignore and not feel a need to know or guilt if I wasn't available for something. But it's worth it. Please give it a try. I am finally there. I don't ask about plans, I don't ask when skids will be around. If they are at the house, fine. If they are not, fine. If DH plans something that involves me, he'd better be ready for me to be unavailable because his lack of coordination with me means my schedule is wide open for me to plan things.

I tell him of my plans so he knows. I don't do the tit-for-tat thing. But if I'm not told about something, I no longer have any compunction about sticking with my plan or not participating.

The side-effect of this lately has been that DH is upset about it and he feels we are growing apart (especially since two of the three kids are out of the house now). Yes, that is a potential side-effect. I, on the other hand, am happier because I am not worrying about things over which I have no say and I have plans to do things I enjoy.

I was just looking at the our family wizard app, for calendaring. Tuesday we had a fun exchange with DH and Munchkin both texting Toxic Troll about the schedule. And then she added she GAVE UP a day because Feral Forger just arrived...but we had only JUST learned of it. Then made a point of "Im givng up my day, but its still my day", so shes getting less # of days...

egads. And I like making plans to go places but have given that up because DH is mr fly by the seat of his pants last minute guy.

So, Ive given up for now. Munchkins schedule is her schedule. Im going to track the actuals, rather than planned. oK, Ill just do my own tracking (for fun!) lol.

The core of all of your posts is anxiety. You're FILLED with it, and I can understand why.

I need to admit that your posts are hard for me to read. They all contain elements of a slow train wreck, and I've tried to wave warning flags in each one because I also married into a family with very different values and a lot of cognitive dissonance. You've married into a bizarre wannabe Kardashian dynamic, where the divorced parents live as though they're wealthy when in reality they're one serious emergency from disaster. 

Of course you're stressed and anxious, and it doesn't surprise me that you're overly focused on small issues. You've married a financially irresponsible man, and he's dragging you down. You're trying to control something, anything, while the train (driven by your H, with BM standing next to him telling him what to do) careens wildly out of control.

What gets me is that you don't assert yourself in any meaningful way to save yourself. You behave as if your're just a passenger, seething but passive. Why do you think that is? Why do you let this man and his ex-wife wreak havoc in your life and jeopardize your future? Why are you too paralyzed to pull the brake? Why aren't you heard and why doesn't your H listen when you tell him there's NO DAMN MONEY? These people are IDIOTS and you know it, but you just wring your hands and distract yourself with trying to micro manage elsewhere.

I know all about anxiety caused by step issues outside of my control. But you haven't done anything to change things or bring peace and order to your life. And until you do, until you get some professional help for you and your idiot H, stress and anxiety are going to be your constant companions. You'll continue to age prematurely, your health will suffer, and your mental health will deteriorate. And that train WILL crash at some point, leaving you impoverished.