I really want to tell you something that is somewhat disturbing. So prepare yourself for this.
I am engadged to a man who has 3 children of his own. His oldest child is 16 yrs old now. when Cody was a small baby, my fiance's wife at the time, well her mother (his mother-in-law) brought it upon herself to tell him and his wife that "Cody was her baby, and you better not forget it." well what a nightmare that has come to. My fiance's in laws took it upon themselves to involve themselves in everything that was none of thier business. Whenever Cody did not get his way, he called "grandma and grandpa to the rescue". ( mind you they practically ignored the other 2 grandchildren).
One day (after my fiance and his ex-wife have been divorced for only 5 years), My fiance got a summons in the mail, that stated that his ex-in-laws are seeking guardianship of the oldest grandson, Cody. Cody at the time being 15 years old, was appearently living with his grandparents. None of which did his ex-wife tell my fiance.
To make a long story short. The ex-in-laws lied in court and stated that Cody had been living with them for 8 years. They have brainwashed Cody into thinking that his father wants nothing to do with him. My fiance went to court to fight for Cody, by then it was too late, Cody wanted to live with the people that bought him everything and let him get away with what ever he wanted.
Cody will not talk to his father at all, will not visit with him. My fiance's other 2 children see him regularly, and they have a very close bond.
I am worried about you, and the situation you and your husband are in. It can turn out to be a nightmare. If something is not done, it is possible your step-child will hate you. Especially if your MIL does not like you. I could imagine what she says to your child about you when you are not around.
(Someone If not you) needs to explain to your husband that some parents still think that thier kids are still kids and want to take over parenting of thier child. This situation that you are in is really not good at all.
If you would like to know more of the story so that maybe you could show this to your husband, let me know. Because my fiance's in laws ruined a father son relationship, and he now has not been able to talk to his son for about 3 years now.
I am praying for you dear. Good luck.