Can I get an emergency temporary custody order of my children if their stepfather is a convicted felon and alcohlic and I suspect my ex-wife is using illegal drugs?
I certainly hope so. Contact your local social services office. They should be able to tell you what your best moves are. I'd also recommend getting an attorney.
Social Services has the authority to remove the children if they're in danger. Even if SS doesn't see it as an immediate danger, your attorney can schedule a "pendente lite" hearing with the domestic relations court for a temporary review of the situation. You will need evidence to prove they are unfit parents.