Thank you for your question.
Since there is a court order in place, he would need to show to the judge why a modification of the existing order is warranted. He could explain a change in circumstance, but overall he would need to explain to the court why changing the existing order is in your son's best interest.
There is a presumption that a child's best interests are met through a relationship with both biological parents, so in that regard he stands a chance of maintaining visitation and/or potentially some custody. However, without a compelling reason, it is doubtful that the court will outright grant sole custody. You will have the ability to oppose your ex' petition, you can attached a declaration from yourself and your son, explaining why the current arrangement should not be changed and/or why it is not in your son's best interests to be placed in his custody. Within the reasoning in your declarations, you could explain your ex' current living situation and the fact that your ex has been unstable and in and out of your son's life. Your son is also of the age where his living preference will be given consideration by the court. Lay out each point objectively and factually in the declaration, try to keep the emotion removed from it.
The judge will look at the petition, the supporting evidence, and any opposition in making a ruling based on what is in your son's best interests.
Please let me know if you have any other questions, or require clarification of this matter. Otherwise please hit "ACCEPT", so I may receive credit for my response. Tips and feedback are also appreciated.
A letter may not be the acceptable format to send to the court. Ensure that you have filed the appropriate paper work, i.e. the opposition to the petition, also. You can reattach a copy of the letters to the opposition, but ensure that you have filed the correct legal paperwork.
If you can show the court that these issues are really not problems, then your ex may just look like he is making a mountain out of a mole hill. If he has bad grades, you may want to show the court how, as the parent, you are addressing this issue. If he crached a tooth, you may want to explain how this happened.
Dental records will mean little without an expert to explain them to the court, but perhaps a declaration or affadavit from your son's dentist would help.
If he owes for back support, then you should definitely pursue that sooner than later.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).