"cough syrup" refers to cough syrup mixed with hydrocodeine. This combination, when mixed with sprite is called lean, purple drank, and syrup. It's heavy narcotic effect relaxes your muscles, hence you move/talk slow.
this may be an exaggeration as he claims to have acres of marijuana. probably not a possibility in the United States as it is illegal and a field of marijuana plants an acre in size would be almost impossible to conceal from authorities.
you are lowering your body toward the dance floor so quickly and your whole body is getting so low to the ground, it's as if I shot you with a police taser gun and the shock is causing this sudden drop