Having had a quick look at your bio and seen that this is a 16 year old boy who is with you 50% of the time - I would have one word of advice to you - disengage. More info at http://www.steptogether.org/disengaging.html

Well firt off if you both are handing him any money don't do it anymore, then your enableing him to get high, second off because he is a minor any trouble he may get into will fall back on BD so he has no business being out all night because whatever he is doing he is up to know good at all hours of the A.M
If he refusses to come home then maybe BD can get him admitted for live-in drug therapey, I would say tell him the doors are locked by 10 and if he is not home by then he had better have a place to sleep, but he is a minor and you dont know exactly what he is doing out there.
See, my BS got involved in drugs really bad, because I stoped handing him money because I found out he was taking pills oraley and snorting xanex, so I STOPED giving him money. So my BS like your SS would stay out all night, know what he was doing? what they call "Licks on cars", he was breaking into cars and stealing credit cards and change or money..whatever he could do to get his high, he was on probation and everything, eventually even house arrest, I put in him program after program, eventually he ended up in jail three times..didn't phase him, now he is in prison and got a year and a day, even still got lucky cuz the States attorney wanted to give him 3 to 5 years, the bill he racked up is over 6,000 dollars thats NOT including the 2,000 I paid out when he was a minor in which I was reaponsible for because at the time he was a minor, and my SS19 the samething same issues( drugs), only he got caught stealing a gun and dealing in stolen property. My advice to you is this: Watch what he brings in and out of the house, does he change friends alot?what kind of drugs do you think he is taking? make sure all your personal meds are locked up or hidden securely "DONT trust him" he has a problem. His moode swings are either cuz he is coming down or has ran out. Next time he is high BD can lie and ask him to go to the store and take him directly to the E.R to see WHAT drugs are in his systume, they can do a blood test then and there. BD can also have him admitted into a rehab because he is a minor. Get TOUGH with him now, or you may end up with a situation like I had, or worse yet wondering if today is the day the police show up and your door cuz SS been shot for dealing with the wrong people or in the wrong neighbourhood, or maybe just cuz you didnt know how SEVEAR his drug use was and he OD. You and hubby need to come up with a plan, and stick to it, this is the best advice I can give you because I been through it for 5 years with my own, and it has taken my son going to prison to dry out and realize what he has done and how he has hurt alot of people and hurt himself, its a hard way to go and hard lesson to learn this way, but you and hubby do everything in your power so if something should go wrong or happen...BD & you will atleast have the mindset to say " I tryed"