H.W.
Sounds like you married a guy who is not going to support you in front of his son. There is no reason you have to take this kid anywhere-- you choose to, just like you chose to marry someone who had bratty kids living at home.
Personally, I'd leave too. Consider it a blessing that you found this out relatively early in your life; you are still very young. You can do better. And you can learn to behave like a grown-up who does have a CHOICE in what she is doing in her life. No one is FORCING you to stay in this situation. You can leave, work, get your own place. There are options.
And for heaven's sake, DO NOT MAKE ANY BABIES with a man who already seems like a failure as a parent.
ETA: You sent me a message saying I'm mean and that words hurt. Sweetie, no one is allowing you to be hurt but you, yourself. What I am exhorting you to do is to empower yourself. You are saying you choose a 'forever' relationship with this man, and that IS your decision-- I am most certainly not arguing that. I also speak as a woman who has been divorced for good reason and has successfully moved on to greener pastures. The choice is yours-- you can continue to do things which you hate doing and making your husband happy, I suppose. But what you are complaining about IS part and parcel of your husband NOT being a good father. Not to be rude, but by the time I was 16, I was able to take the bus anywhere in town on my own and worked an afterschool job-- and I had *really* screwed up parents. I would absolutely NOT have children with someone who felt it was okay to permanently infantalize their kids. That's not being mean, that's common sense. You are 25 now. Do you want to be 45 or 50 and having to get an job to support your 20-25 year old? Because the writing is on the wall-- marriage does not automatically make people change. Don't expect it.