Hi Pivot - You addressed Hiram but I will go ahead with my own comments to your post.
As to each of your analogies - ( the husband leaving the family; the wallet in the dark alley; the sociopath who escapes detection) all of those are difficult cases, but still not exceptions to the rule.
Let's up the ante - a sociopath develops a method of spending his entire life killing innocent babies for fun, but due to his method is never caught.
Does that change the fact of nature that there is no supernatural god? Does that change the fact of nature that there is no evidence to support any kind of "ideal form" or "essences" or "virtue in the air" to which to look for a standard, those remain invalid reference points.
What Epicurus was saying was that in the absence of valid "absolute" reference points we must look to whatever Nature gives us as a guide, and ultimately she gives us nothing more than pleasure and pain by which to judge the desirability of all things.
So in each of your examples it is entirely possible that results that we consider "bad" may take place, but that doesn't mean that there are gods or absolutes of any kind that tell us that we are right and the "bad actor" in any of those cases are wrong. If we think that some mechanism ought to be in place to discourage those results, then we organize communities and nations and police forces and armies, to enforce those rules, but in the absence of our doing so, there are no absolute forces anywhere which will enforce our preferences for us.
So that is one major aspect of what is going on here, about which Epicurus was realistic.
And so when you reach points such as "It just seems like this sort of valuation, as a means to an end, is the wrong kind." The key issue there is "wrong kind" - and the question is "Wrong by what standard?" Epicurus rejects false standards that do not really exist except in our minds, and Epicurus suggests that if we wish to look for "justification" for our own view of right and wrong, we can look nowhere else but to Nature if we
want some kind of sanction outside ourselves. And the only guidance Nature has provided - to all living things - is the faculty of pleasure and pain.