The writeup on Section 31 is very good and was following along until you listed almost every couple on DS9 being in toxic relationships. Maybe you’re confusing relationship conflicts with toxicity? Maybe I don’t know what toxic means.
I’m pretty good at seeing different sides of an arguement, but you’ll have to do a lot more convincing on Kira/Odo, Jadzia/Sorf, Sisko/Jennifer/Kassidy being in toxic relationships. These relationships work for me because they are trying to overcome cultural and professional challenges. One character might not budge on something but overall they try to work things out.