I would suggest to him through examples perhaps in a letter the specific behaviors so you can be clear. There is no gain in accusing him of doing drugs and he won't admit it anyway if he is in denial. However, if you can sit down with him and let him know you are concerned with his behaviors and his daughter being around his mood swings, he might be willing to at least go to counseling with you if he knows you will not tolerate the behaviors. I wouldn't confront the other person. That will just get messy. It is how you react that will ultimately set the stage for motivation for him to change how he is acting. It sounds like you both could use some communication skills to enhance your relationship. We don't come with manuals you know. ( ;