Your husband is enabling his son's behavior. Your SS needs help. I had friends who ignored this behavior and believed their son when he said he was "just delivering" not actually using. It wasn't until he was arrested, beaten up by the higher up dealers, and in the throes of full blown addiction that anyone stepped up to do the right thing. The kid didn't finish high school, is in his second stint at rehab, and has lost tremendous opportunities.
If your SS is involved with drug dealers, you and your family are at risk, and your possessions are likely to be stolen to pay drug debts.
A member of my husband's family was similarly involved, and we banned her from coming here because we had a child, Grandma's silver, and so on. We did meet ON OCCASION in public places where we could see if she was followed (drug dealers are also often in gangs - this one was, with many arrests, firearms, etc.) and we always took phone calls, but we could not risk the hard-core people knowing who we are and where we lived.
You and your husband have to get on the same page, or you have to turn your SS in to the authorities. If your husband thinks his son will stop this if he gets to play enough golf, he's sadly mistaken. Short term, join a support group like Al-anon or Narc-anon to learn how to cope. It will give you strategies that work and help identify those that don't, and also acquaint you with laws, resources, and consequences.