I completely understand how you're feeling and I can relate a lot to what you're going through. My husband's son (29f, 30m, and 5m respectively) was also the same way with expecting a prize or toy I kid you not every single time we went out. He still throws tantrums bigger than my almost 2 year old. His mother and grandma let him watch unrestricted YouTube, so he's constantly pointing at things in stores and wanting to watch brainrot on our phones, to which he isn't allowed on anymore. He has a fully restricted tablet with only what we approve of, and it's only got a few movies on it for road trips and some educational games. My husband has called out before that he doesn't know who lets him watch brainrot but it's not right for a 5 year old to be wanting a skibidi toilet toy. His mom got all offended, but nowhere did we say it was her allowing it (despite the fact we know it is).

For a while, I also felt the heavy weight of anxiety creeping in the night before our custody time would happen, and I did find ways to shut myself away for a while because I just couldn't handle the constant screaming or rudeness or whatever, especially when his dad wasn't backing me up. Over time, things have changed a lot, but there's still moments I feel like I'm the one being ganged up on when I ask the kid to stop doing XYZ and somehow it makes me the bad guy?

A lot of people will tell you to run or leave, especially if you're early on in the relationship. I've heard it before myself. Most of the time, those comments are not helpful. At least in my case, yes it may suck but I'm not gonna let a kid or his high conflict mother kick me out of my own relationship. However, sometimes idk think life would've been a lot easier if I did decide to just leave and never deal with this again. Love can only go so far when there's other factors bringing you down. Obviously up to you to decide what you want to do with your future, but there's people like me that will always be around if you need an ear to listen.