You stated that people are coming and going quickly. I think they are dealing. It probably takes about 10 minutes or less to make a sale. A little longer if someone is sharing some before or after. Yes, I used to dabble, strickly party favors.
Definately call the police everytime it's loud. Then call the landlord right after. I don't care if it's 100 times every night. The police will show up if you keep calling. The landlord will do something if you keep waking him up. You have to stop being nice and not wanting to seem like a pest. You have a child and neither of you can sleep. Be civil when you call, but be firm. If either gets nasty with you, take a deep breath and stay civil. Tell them you will stop calling when the noise stops.
Document all conversations. Date, time, what they said, what you said. If something isn't done take them to court. You could end up owning the property. Then evict them, tear it down and fence it in, put up a playground for your daughter.
I just had another thought. Contact the Attorney General for your state. File a complaint against the landlord. I bet he won't like getting a letter from the Attorney General. Again, document everything. In fact, get a notebook just for this so that everything is in order, page after page. I can't stress enough how important it is to document it in detail.
Good Luck
