It's very difficult for an attorney to put percentages on a custody case. In addition, it often requires looking much more closely at the facts than what is doable on a legal advice site like this.
Disclaimer: This email message in no way creates an attorney client relationship between Majeski Law, LLC and the recipient. Responses are general in nature and do not constitute legal advice. You should consult a lawyer regarding any specific legal matter.
In order for a change in custody to be considered, you would have to show a substantial and material change in circumstances occurred since the final order was issued. The burden of proof is high and the best interests of your child will always be the court's overriding concern. To properly assess your particular situation, I suggest you consult with an attorney to thoroughly discuss all of the details surrounding your case.
If this answer was helpful, please mark it as helpful or as a best answer. This answer is for general education purposes only. It neither creates an attorney-client relationship nor provides legal guidance or advice. These communications are neither privileged nor confidential. The answer is based on the limited information provided and the answer might be different had additional information been provided. You should consult an attorney in your area.
As my colleagues have stated, there is a burden of proof for switching custody once an order has been enacted. His interference with your relationship may rise to the level of being enough to request a modification based on a substantial change of circumstances, but your best bet would be to consult with an attorney to properly advise you based on your specific set of facts.