iseult, ive found on this thread you will get some very open and honest answers. They may not always be what we want to hear but they will be real and honest
I know you had mentioned that the reason for the marriage was not for the visa but you seem to be very stressed about them "shipping" you back. You are not a product that they can return. You are a person so it might go a long way in realizing that if the relationship ends they wont have the power to force you to leave.
Even if you have to come back to the states it will be because your visa has expired and not because of them.
Im not sure how old you are but I would focus on getting better. Your health should be the most important thing right now. I understand the world crumbling around you but you cant control him or his family and the way they respond to this. It sounds like from their reaction this is something they were aware of but didn't realize the extent of it.
Your recovery should be number one, regardless of where you end up at least you would be healthy. Good luck