Actually, any employee is within their rights to set their own hourly rate, regardless of if W-2 or 1099. It's up to the employer to decide if they want to pay it.
Now if you are the only person who can work an event, than the employer is stupid for not having a much larger pool of employees to chose from. If I were your boss, I would have told you to get bent, and worked it myself, and then worked on bringing on additional contracting staff.
As to the OP, I would add suction, oxygen and defib/AED to the list of equipment. If you are providing BLS coverage, you should actually have the equipment to treat to that standard of care. And once you calculate the cost of that equipment, you see why people are saying your employer should be providing you what you need.
Based on what you listed, it seems like all you were bringing was a basic first aid kid. Does your county have a list of required equipment for standby EMTs?
A 1099 wage is 'per job done' vs a W2 which is 'per contract'. And I'd like to see an EMT trying to purchase a D-tank for private use, not to mention an AED or portable suction.