Evan, you are *probably* correct in that the promoter's insurance would be primary... that is, in the event of injury to the public, the facility, or the entertainers, 24-7's policy would be the first in line.
However, their insurance company could come after you, if they thought you (your company, or anyone representing your company, even without your knowledge) did anything that might have caused or contributed to the loss. Those who experienced the loss (victims, surviving family members, etc.) could still sue you, too, but keep reading...
There is also some interesting legal turf here, too.. you are a minor and can't legally enter into contracts, nor be held liable in a civil court. The result is that your parents/guardians could be held liable for your actions, errors, or omissions.
As I am not an attorney, I could be wrong. I could be right, here in Kansas, but wrong in Maryland... You and your parents should seek proper legal counsel regarding contracts and liability. This also goes for Tom, as he partners with you, but you aren't able to legally enter into a contract with him because of your age... So you and Tom do a gig together, and someone gets hurt or their property damaged. Because you are a minor, Tom could easily end up bearing the entire cost.
I'm with Winston. I'm not parade raining... but this is something you need to learn about. You'll need this knowledge anyway, when you turn 18 next year.
Good luck, have fun, be safe.
Tim Mc