From what you've described, I'm not seeing much in the line of legal options to change up the custody. Maybe your lawyer would advise you differently. I doubt it, though. My attorney in my WI divorce advised me that courts will generally not be very interested in re-evaluating custody in the first two years of a divorce, unless there's legit evidence of child abuse or suchlike.
I can see where there was a lot of drama. Your divorce was finalized 15 months ago. You were in a new relationship before you were divorced, and dad already had both a new relationship and a kid at the time of divorce.
No matter how you slice it, though, there will be coparenting, and there will be transfer days. You and dad have got to figure this out.
It can get better. My coparent and I were text-only for a time, and now we're friendly. That process took about 5 years. A book that I read that really helped my end of communication was Joint Custody with a Jerk. Amazon link: https://www.amazon.com/gp/product/0312584202/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I’m not sure if this is helpful, but I’m throwing it out there because it’s often recommended by my colleague: https://www.amazon.com/Joint-Custody-Jerk-Uncooperative-Hands/dp/0312584202