1. Yes
2. Yes
3. As it pertains to morality, questions of right and wrong can be explained with happiness and suffering of living beings. This is what makes it self-evident as it pertains to how we treat other humans. If we are in a position to affect happiness or suffering of others, we have the moral obligation to do so. Consequently, these obligations have found there way into civil and criminal law. Applying the golden rule doesn't necessitate that it came from a omnipotent being, or that one is needed. Empathy works just fine, and anybody that does not have some basic sense that cruelty is wrong to begin with, certainly won't learn it by reading it.
Take the Nazi or child rapist example. How could one do such a thing to other humans, while maybe being a decent human being in every other facet of their life cannot be explained as wrong just because god said so or because it was (or in this case we have to assume wasn't) imparted on us by him. The simple explanation is the people that were the targets for the abuse simply weren't objects of their morality. In the case of the Nazi, they weren't even viewed as humans. Anybody that understands these actions as morally wrong obviously have a basic sense of empathy.
4. See #3 about happiness and suffering and empathy. If morality or ethics represents a set of knowledge, then it should represent the potential for progress and regress as well. From a biblical worldview with stoning and genocide and slavery, even you should appreciate this.