There is no such thing as a debtor's prison. The creditors have a right to get a judgement in court. Then they will try to collect, but you must have something they can get at, like job=wage garnishment, bank account=levy or real estate= lien. If none of those apply, you are judgement proof. Bankruptcy is a federal court jurisdiction matter. The length of your residency only determines which set of exemptions will be applied to your assets to exempt them out of the bankruptcy estate. So you can file if you want, but based on everything you said so far, you do not have to. I advise my unemployed clients to consider waiting. If you get sick, and I assume you do not have a health insurance, then you will accumulate new bills you cannot discharge in chapter 7 again for 8 years. When you get a job you can file to protect your wages.
As a general rule, both parents are responsible for necessary medical treatment of minor children, however, leave any 'generalities' aside -- if you were sued for this bill, and they LOST the civil lawsuit (ie YOU won and the Court refused to grant a judgment requiring you to pay) and they did not appeal, then you don't have to pay. Period.
I strongly suggest that you tell the collection agency that this is not a valid debt, and request 'verification' of the debt in writing, and that they ONLY contact you in writing from this point forward. If that doesn't stop the harassment, you can sue for their violations of the fair debt collections procedures act. You can also request that Equifax/Experian/etc remove this false information from your credit history by following the steps set forth at web link below. And be careful -- this link is the 'legit' one -- there are lots of 'free' credit report sites that will charge you -- this one is free once per year and with no 'catches'.
If you don't get anywhere with this, I strongly suggest you find a local attorney who can help you through this process. Good luck!