I suspect the
I suspect the bakeshop employee.
Reasons:
He is “very worried” yet he didn't check when the customer didn't pick up the bread yesterday (even though the door isn't locked). There isn't any furniture in the room, possibly because it has been stolen. His guests for which he ordered the bread are probably the boy and the girl. But, they were invited for a drink, not for breakfast. Did he expect them to stay over? That's very unlikely. Which leads us to the question: why didn't his guests for who he ordered the bread notice he was dead? Which leads me to call the truthfulness of the baker's story into question. It wasn't suicide; the ceiling is high, and if a ladder was used by the customer it should have been carried away by someone. The broken bottle of beer may have been dropped by one of his guests (the boy or the girl) when they left.