Did Epicurus claim that any single act of injustice (no matter how small) ruins a life through constant anxiety unless caught or turning oneself in, or is he primarily targeting those who engage in injustice as a recurring pattern or stable trait being filled with fear because they constantly violate the pact?
To your original question above: I'm concluding (perhaps from ingnorance) that these PDs and VSs as well as interpretations of Epicurus' meanings are generally focused on why you shouldn't do unlawful or unjust acts that are immoral is because you won't be able to live happily since the pain will outweigh the pleasure of feeling good about yourself.
I can't get away from a belief that laws and morals are not REALLY established by social compact. Obedience to laws is by social compact, but the laws are not created that way. They are established by those who have power withinof the community by lineage, or military or economic might. Is there an objection that in a democratic system that can't happen? I hope a comparative study of power politics today, will show that power was exercised in Epicurus' time too by virtue of power exercised by wealth etc in the same way. THEREFORE a discussion of just or unjust laws is missing the point within this discussion topic.
Lastly, I've always taken this PD 35 with a measure of salt. Our mental power of rationalizing allows us to violate every law we've ever violated. And our capacity to forget over time, allows us to suffer less and less over time. And don't forget the concept of self foregiveness which itself is a major factor in it's use or abuse. I'm not in favor of saying people are evil or stupid for thinking they can get away with it. But I think if you balance the real and potential pleasures of life actions against the real and potential pains of one's actions in life, that is still powerfully within Epicurus' message.