Advice For Custody Issues Across State Lines

I’m trying to support my partner, he did not have legal representation when they divorced I have been in a stable (closed) polyamorous relationship since 2019. My partner, who just retired from the military after 20 years this week, has been consistent in paying his child support, medical, and dental for his daughter since his divorce in 2011 and visiting his daughter based on their divorce decree. Beyond the required child support, he also pays over $300 monthly for additional expenses like braces and extracurricular activities for his daughter, which is not in their decree.

In early 2022, his teenage daughter (who lives with her mother and her boyfriend in Texas) expressed her desire to move in with us due to an unhappy home life. She shared issues like being exposed to excessive drinking and fighting at home and emotional neglect from her mother. When my partner shared these concerns with his ex, communication from her mother became strained and hostile. We had to advocate for therapy for many months before his ex decided to get their daughter into treatment. His ex has been very adamant about not wanting her daughter to move in with her father, always having an excuse even though the divorce decree says at 14, she is given the choice to live with whom she wants.

Now that she is 14, her mother is preventing her father from seeing her for those 30 days this summer. Her mother has blocked all visitation efforts with excuses. She has been making derogatory posts on social media about my relationship with her father, claiming I am an unsafe person for her daughter because I am polyamorous. Completely fabricating stories that indicate that I (we) are unsafe for her daughter, and texting us at 9:45pm with odd and incoherent text messages. This has never been an issue in the past. As a family (my partner, his daughter and myself) have seen each other every summer for those same 30 day visitations, traveled to her her to visit her sporting events, and gone on vacation for Christmas and Thanksgiving every other year since 2019.

We know we need an attorney, but this is new territory for us, and we're unsure where to begin. The financial disparities between us and the child's mother are significant. She and her boyfriend live a high-end lifestyle, including multiple luxury cars and vacations, whereas we drive the same cars we had in 2016, and I cut down to part-time to go attend graduate school last August. We're concerned about our ability to afford adequate legal representation compared to what they can secure.

Since the divorce finalized in New Mexico and his daughter and ex-wife live in Texas, and we live in Florida, what legal recourse do we have to address the visitation issues and potentially modify the custody arrangements now that my partner is retiring and income is lowering?