Oh man! I do not look forward to this stuff! I really feel for you.
I think your talk was great! Being honest about it in a calm matter was right on point. I do think there is a way you & H can meet in the middle. Bottom line is its illegal & you could get in trouble since its in your house. I would definately have consequences if it is found again and I do agree with your H that the other parents should be contacted. But, you could meet in the middle by telling S15 that us what will happen if drugs are found in the house again. As an ex pot smoker, I will personally have a similar talk with my children & have zero tolerance for anything illegal in my home or vehicles.
I could only imagine how frustrating it must be to have H spout off his opinions...but never address them himself. Hopefully he goes to IC with you, because a united front on these issues especially will be important.
You did great, Ad!
M: 9 yrs T: 13 yrs H:34 Me:35, S4, D2, S 7 months Dday 11/12-PA & multiple PAs Dbing 12/12 S 1/13 7/13 H moved back in basement. 8/13 #3 born 10/13 still cheating 10/13 He moves across country, I file for D