In my opinion what you're experiencing is not neuropathy caused by nitrous oxide use.

The neuropathy seen in people who abuse nitrous oxide takes months and even years to become clinically relevant because nitrous oxide is not directly damaging your nerves or spinal column, it is disrupting the processes responsible for proper nerve function which take ages to cause a clinically significant effect. Experiencing neuropathic symptoms hours after use completely rebukes all research into how long-term nitrous oxide abuse damages the nervous system.

Did you use any other drugs before your symptoms started? It sounds to me like you slept very heavily and potentially pinched a nerve in your arm which is now affecting your mobility. It is a known phenomenon seen in people who take high doses of strong tranquilisers and then pass out in a position which either pinches a nerve or restricts blood flow to the extremity. What were you told at the ER?

Additionally, for a little bit of perspective, consider that thousands of people across the world today will use nitrous oxide under medical supervision and will be taking far more than the equivalent of 4-5 chargers worth without experiencing neuropathic symptoms. If this was a common issue nitrous oxide would not be used the way it is.