1. It's my understanding of the present state of affairs in most countries. Apart from religious law, it is rare for criminal statutes to include a clause like "No person shall murder another." People do tend to interpret "Murderers shall be put in prison" as "Thou shalt not murder", but IMO the latter is an assumption behind the law, not its content. All the lawmakers already assume that murder is wrong. The law's job is to decide how to discourage murders, what to do when murder happens, etc.
2. The set of objective moral imperatives that exist at all times and places, and their application in particular circumstances, should exhaust the set of all the moral imperatives that we are ever obliged to obey. By "all times and place" I mean "even in times and places where the state does not exist", because that's the condition in which humans lived for the majority of their existence on Earth. So I don't think it even makes sense for there to be a moral imperative that only exists in certain circumstances (e.g. the state) unless it is an application of an all-times-and-places moral imperative. But I cannot seem to find an all-times-and-places moral imperative that could be applied in such a way as to justify obedience to the laws of a state just because they are the laws of a state.
3. Bad example. What makes you think it is morally permissible to steal something just because the owner had obtained it immorally? (Two wrongs don't make a right, etc.)