Barring a situation where your mother has a guardianship over you (which you would most definitely know about) you legally become an adult upon your 18th birthday. Which means, barring the guardianship situation you are under no legal obligation to follow your parents' wishes.
However there could be long term consequences for completely disregarding your mother at 18. Although you are an adult you do not know everything and would be wise to at least respectfully consider your mother's...
It seems as if most towns in Massachusetts have those intersection cameras, if the intersection had one I'd seek to have the attorney provided by the insurance company subpoena the records for the date of the accident.
As was previously suggested you could seek a 209A Restraining Order against your ex. If that is the not the method you which to use, although it is strongly advisable, then you can get an affidavit from your children stating what they heard your ex say in regards to having someone injure you. Affidavit forms are readily available online and must be notarized, which can be done at a local bank in most cases.
Best of luck in a difficult situation.
The charges pressed will be at the discretion of the local district attorney's office, however since he crossed state lines it would constitute federal jurisdiction as well. He could possibly be charged with kidnapping for taking a minor across state borders without parental permission. If he engaged in sexual relations with her charges could stem from that as well.
Best of luck.
THIS IS NOT LEGAL ADVICE AS I AM NOT LICENSED IN YOUR JURISDICTION
First, contact a local attorney who specializes in divorce to discuss this further.
Second, if you do not have the cash to pay $25,000 up front and cannot afford an attorney, attempt to negotiate a payment plan that you reasonably believe you can afford with her attorney and attempt to get a lower interest rate then the 10% stated by the first responder to this question.
If she were given judgment against you for $25,...
Send a certified letter and email telling the lawyer he is to cease work and to file a motion to withdraw from your case. Furthermore ask for a detailed copy of his bill to check the expenses and billable hours he is claiming. If they do not seem proper question him on it and if necessary contact the Board of Bar Overseers to report misconduct.