Twinkle, 7m to get over the love of your life leaving and shacking up with an OW? It's going to take you longer than that! At least you have MN now!! 
The entire rug has been pulled from underneath you hasn't it. The baby thing and then the affair, what a bastard.
you are 30? tough age to take all this on by yourself. when you hit 40, you take a lot less crap from people and you'd tell the IL off for being so spineless and disloyal to you. Take it from me, this almost 43yo gimmer here! 
Would it help for you to withdraw from the lot of them for a while? suspend the overnight visits, stop the child care, just until you establish YOUR new routine. H can see DD for a few hours once a week, but that's it. You need a month or 2 off.
Then once you have realised that actually YOU call the shots now in your life, then you get to say when access is. You get to say, no, no overnights with a woman that is only in your H life a matter of months. you don't care where he lives or with whom or why, but there is no contact with a casual partner, not until they have been together a proper amount of time, and to be honest, not until your DD is old enough to understand. No weekends away, no holidays for the foreseeable future.
Your H doesn't deserve to have this playschool happy family shit going on, he ripped the life out of your marriage and you are being expected to just go along with it all. No wonder you are still livid!
ADD to this his parents opened their arms to HER and you are left out in the cold again? NO! this is not a family set up I would want my DC exposed to.
Take a deep breath and stand up, say NO. Once you start feeling that you are back in control of your life, the anger will stop building, and will eventually dissipate.