Thanks for clarifying your situation.
Unfortunately in my opinion unless K is willing to work on things and set some boundaries with his OSO there is nothing you can do.
I personally hate the whole primary secondary relationship model. To me the secondaryends up feeling like a second class citizen. I live by the rule of never make someone a priority who makes you an option. My relationships are separate but equal. Butch's wants do not come above Murf's.
Since K is not going to work to make things better my advice is to do what is right for you. You deserve happiness.
Late 30's staight female
Married in the eyes of the government to Butch since 2001...
Murf my second husband has been with me since May of 2012.
In a V relationship with an average 60/40 split of time. Only due to Murf's and Butch's crappy work schedules.