my two cents

1. You choose to post your questions in the law forum but not the forum of myhouse. I think you want to know your right and duty by law as a step-mother, what you can do and what you cannot, what you can request and what you cannot... In this case, I think you need to have a consultation with a lawyer for half an hour or 1 hour. He/she will help you to protect yourself well.

2. From ethical part, here is what I think.
a. Your husband does not respect you. You need to let him know that hurts your feeling and your relationship.
b. If your husband is your 2-year-old son's biologic father, ask your 2-year old son what his feeling is about his stepbrother and the way his father treats him and his stepbrother. I don't think a 2-year-old child will lie. Let him tell his father. Your husband will be less defensive if this is from his another son.
c. If I were a step-mother, I would not discipline my step-son until we have accepted each other. This means we need to give our love and care first before we can ask for something. I would treat him as a guest or coworker.
d. Ultimately, your husband is the key point. Win your husband's heart and you win everything.
e. Something you may consider here as a reference.
昔日寒山問拾得曰：
世間謗我、欺我、辱我、笑我、輕我、賤我、惡我、騙我、如何處治乎？
拾得雲：隻是忍他、讓他、由他、避他、耐他、敬他、不要理他、再待幾年你且看他。