Sorry about the trouble you're experiencing at home. You've already been given some terrific advice, so I'm not going to repeat it.
I just want to add that if you're communicating your needs clearly, respectfully and lovingly to your SO and metamour, and can't get any traction with them to resolve the issues, it's time for you to up the ante. From what you describe, you are not being heard. Maybe it's NRE, maybe it's that the current situation is working really well for them (and why wouldn't it, with you doing so much of the work for their enjoyment?), maybe it's something else altogether. Whatever it is, you will never get what you need from them until you first get their attention. So, get their attention! Especially his. Call a meeting, write a letter, bang a gong, blow an air horn or whatever will work, but call their attention to the fact that this relationship is in trouble!
And once you have their attention, express your needs clearly and directly, and ask for what you want. Then you can work with them to see to it that EVERYONE's needs are met within the relationships, including yours. It's not all that complicated, once everyone's focused on resolving the problems. But the first step is to bring it to their attention.
Good luck to you all.