I realize dealing out consequences to a difficult child is much different than a easy child. You really have to pick your battles.
Do you want to allow him to do this act (leaving the house without your knowledge and walking to school without your knowledge and skipping a field trip with out speaking to you about it and being with an undesireable friend) without a consequence? If you think this is not a battle worth fighting than let it go.
If you think this is a line he should not cross then come up with a rule about leaving the house and what his requirements are upon doing so, IE: must ask you if it is OK, must be sure that he will be on time, etc. Once the rule is clear for him, if he breaks it there must be a consequence for breaking that rule. Let's say it is cleaning the toilet daily, or doing the dishes, or whatever you would like him to do that he hates doing LOL.
It is OK if you choose not to dole out a punishment for this time because the rule was not clear, but next time... He also has to be willing to sit down and have the conversation in a rational manner and admit that he understands the rule and the punishment if it happens again. Otherwise he gets the punishment this time.
Work together on it. I think this will be very valuable for the two of you. Even if he wants some input on the rule.
I realize this is not what everyone would suggest. But, you guys are kinda starting over and it has been rocky. But, maybe it is because he just does not understand yet. Get some house rules that you both can live with.
I would start out with this one and see how it goes. If it works then tell him you would like to come up with a set of plans for the rules and consequences. I would start with deal breakers (drugs, sneaking out, etc) and get him to understand why they are deal breakers (PO, safety, etc).