In most countries there are very strict regulations around storing chemicals in labeled and approved containers. I would be surprised if the US doesnt have similar laws, but training and enforcement of such things definitely seems to be a lower priority over there.

The vent is for the moisture-laden warm air that results from forcing hot air into it. Possible than vented dryers are less common in your region if you are not familiar? They are an incredibly simple design, and thus very cheap to make, but are significantly less energy efficient than modern condenser or heat-pump dryers.

Is it possible that the nut is reverse threaded? Ie, clockwise to undo it?