It is difficult to tell from your question whether the divorce paperwork has been transferred to Florida, or if it remains in Maine. If you have sole parental rights and responsibilities, he may have no right to say where the girls live. Further, he cannot stop YOU from moving. Therefore, unless there is a court order stating otherwise, you may move to Pennsylvania. You should ask an attorney to review your divorce judgement to ensure you understand exactly what rights you have.
While I agree that you and your spouse may both need attorneys, you may want to look for an attorney in your area that focuses on "collaborative divorce." This will allow you to begin the process with the understanding that you both agree to resolve conflicts by employing cooperative techniques rather than adversarial strategies and litigation. Another option is for you to attend mediation with a divorce mediator, who can help you determine whether you actually agree on all the contested issues.
Without a written agreement, or contract, it is unlikely that your agreement will be enforced by a Judge. However, if your ex-friend decides to pursue this in Court, you must be sure to respond and participate in the action. Otherwise, you face having a judgment entered against you.
As Attorney Kenyon said, the decision to prosecute is up to the District Attorney, who also decides what sentence he or she thinks is appropriate to recommend. You should contact an attorney to ensure the District Attorney is made aware that you do not want to see jail time.
You will need to file a Motion to Modify the divorce. The forms and what to do with them can be found on website of Pine Tree Legal www.ptla.org. Convincing the Court that a change from shared residence to primary residence will require that you prove that doing so is in the children's best interest and is not something that can easily be explained. You should contact an experienced family law attorney to discuss your situation.
Depending on what your desired result is, you may need to contact the local police and/or an attorney in the State in which the ex lives as it is may be that Maine does not have jurisdiction over the ex.
Child support is based the income of the parents, and the ages of the children. If you have an order, you may be able to modify it going forward, but you cannot modify it retroactively. Therefore, what you currently owe must be paid.
If you have parented the children for a significant amount of time, you may be able to petition the Court to award you rights of the children as a de facto parent. You need to consult a local attorney to discuss your options.
Your child's biological father will not be able to avoid paying child support simply because he has significant debt. You will need to proceed withe the parental rights and responsibilities case to allow the Court to determine child support, as well as parental rights, residence and contact. You should contact an experienced family law attorney to assist you.