Ok, you're not crazy, and I've definitely felt the same way at times. However, I'm not entirely ready to completely discredit your SO. Being a stepparent takes SO much communication, and it is really tough. But remember, this whole situation isn't just hard on you - it's hard for him, too. He will always have some sort of relationship with his child's mother, which means he has to make decisions without you at times, and try to keep the peace with her for the sake of SS. I've accepted this as reality, but that doesn't mean it's easy to deal with - it's definitely not easy.
Dinner out before hand (and I constantly have to remind hubby not to call it a date) and he drops it on me that we are taking SS to his moms house afterwards.
This sounds really frustrating. One area where I really excel is foresight/thinking ahead, and when other people can't do it as well as I can, I get really frustrated and angry. With that said, people make mistakes, and not everyone has the incredible ability to think ahead like I do. Is it possible that this was an honest mistake on your SO's part? He has probably had a full day, just wasn't thinking about it, and didn't realize it would be a problem for you. That doesn't mean you should just let it go - but you should address this situation specifically, while remembering that this might have just been an honest mistake. Let him know that next time, you would appreciate knowing the plan with matters that concern stepkid, so you are able to choose what you would and would not like to do.
He didn't tell me BM kept his name until after I changed mine-he took that choice from me. Is this something you asked him about before changing your name? If you didn't know this would bother you until after it happened, then how do you expect him to know it would bother you? I was kinda pissed too when I realized I wasn't the only Mrs. Ihcun in the world, but I felt like that was on me, not on him.
He took away Christmas traditions, left me out to spend time with SS. He takes my choice of free-time on weekends with SS "Kiwibird go play games with SS" (if I wanted to play video games I'd ask....and I'd want to a lot more if I wasn't pushed).
Yes, that sounds controlling and unfair - but it takes two to tango in this case!! Step up your communication game and talk to him. Your concerns are totally reasonable, and if he's a good SO for you, then he will listen. How did he take away Christmas traditions? Did you ever tell him that certain traditions were really important to you?
And oh my gosh it's so important that you get personal space from stepkid. But you have to tell your SO that - "I do not always want to play games with SS. When I do, I will approach him and ask if he wants to play - but I am not his babysitter. I am not a place to send him to when you want him to do something else."
I'm so sick of having choices stripped from me
I would be too!! But you are an adult, and no one is making you sit there and take it.
For me, being a stepparent and wife has been a huge learning curve. There are new things I'm discovering all the time that totally, irrationally irritate me. It's a lot of self-discovery, and it's been important for me to avoid taking it out on my SO. Ideally, your SO will support all of the thoughts you have - positive and negative. But to end up in the bathtub shaking from anger at his stupidity (trust me, I've been there) isn't healthy. It needs to be fixed, and the change needs to happen with you first.