Husband is threatening to turn my son in to CPS for smoking pot?

Although my 16 year old son probably experimented with pot a few times, my husband of four years (who is not his father) thinks I haven't done enough to stop him. I have never condoned or allowed my son to smoke pot. I have never found pot or anything in his room, but my husband says he smelled pot on him a few times. My husband does not care about my son - he threatens to call CPS when he is angry with me or my son for doing or not doing something completely unrelated to any purported pot smoking. For example, my son was supposed to mow the front and back yards and called me at work to ask if he could go to the park and finish the front yard after I got home from work. My husband found out and threatened to call CPS. When my husband and I had an argument over the phone and he continued to call me on my cell phone, I stopped answering. The result - he left a vm threatening to call CPS. I have copied several voice messages onto a tape, and took photographs of the text messages, because, guess what, he threatened to have my cell phone shut off. My husband says that CPS told him that if he calls them, they will come and drug test my son and if they find marijuana in his system, they will take him away from me. I told him they would most likely drug test US, not my son, which I would have no problem with. I should add that our house is on the market and has been for a while, I am waiting for it to sell before my son and I move on to our own place. I am on the mortgage and I cannot afford to pay both the mortgage and rent and cannot afford an attorney right now. Also my job would be in jeopardy if I do not pay my obligations. My husband is using this to control me. So, my question is, would CPS take my son away from me if he had marijuana in his system?