I see where everyone is coming from with the idea of just stepping back and letting him do it all/going out with the baby. For whatever reason that I probably need to work on, I don’t feel comfortable doing that.
He has an issue, but he’s comfortable enough not to resolve it in the most obvious, clear and timely manner.
You have an issue, but you don’t feel comfortable resolving in the most obvious, clear and timely manner.
That’s a deadlock. Which in the longer term could knock holes in the foundation of your marriage, which risks potential longer term negative consequences for your child.
Having ADHD doesn’t make us incapable of taking advantage of other people’s reticence to make us the primary cleaner upper of our own messes. Given that there is likely a genetic component and girls can have it too < waggles self as evidence > it is not in your best interests to prioritise avoiding discomfort in the now. Not least because if the smallie has inherited any tendencies you are going to need extensive practice with all the right tools to give her a headstart in learning how not to fuck up quite so much in life.
It’s not fair, but it is realistic. You taking on the discomfort of “your mess, you deal with it” (and whatever rhubarb in-laws believe/talk themselves into believing about you) is your best foot forward in getting what you need from your husband in terms of consideration. And it’s good practice in case those genes are going to feature in your parental future.
I wish you well and all the luck on offer. I can live with being adhd+me, but I’m not sure I could cope with being married to adhd+me.