Unfortunately the addict will always be able to find a dealer, even if you locked this one up he'd just find another source...
I'm sorry you are dealing with this, it is so hard. Try to protect yourself and your child. Take time to decide if YOU think it is ok or if you can put up with him being high under your nose or around your child or in your house. Because ultimatums won't stop him...the only thing you can really honestly change is you.
hugs..