For a couple to accept that and to negotiate other partners in a honest way does seem like a good thing. But from my perspective, my position in this thing has many negatives and very few benefits.
I'm sorry your situation is negative for you and are treated without a voice in the things that concern you. You sound like you DO want a voice in the relationship. So...why accept these terms? If terms don't meet your needs?
Ultimately you are responsible for your health and well being. What's your plan to get out of this situation now that you have become aware that polyshipping could be executed in a more honest, open fashion? You don't sound happy in this situation and some of your needs are going unmet.
Could choose to do something about it.