Hmmm. I sense an awful lot of game theory and "strategery" going on in your thinking and re-thinking. One up or one down sort of territoriality. I can't function very well in these scenarios and I end up losing my bearings and making a lot of mistakes, stepping on toes, missing my own intuition and being generally fairly miserable.
I tend to go into these "what if" scenarios out of fear. The antidote to fear is love. Unconditional love takes a willingness for me to open my heart and just let go of fear.
I don't think the primary is at any disadvantage, as from my experience the SO and the "secondary" end up having just as many "relationship issues" as the primary and SO do. People are complicated. It is your privilege to love TP unconditionally and to be there for her when the shit hits the fan with her "secondary." :-) (Personally, I'm not sure primary and secondary and tertiary are really accurate. My experience: the lover I am with at the moment is my primary. I realize this is a hot button issue on the forums and this is just my opinion).
I think it's a curious opinion, that women have it easier in poly situations. I have heard the exact opposite expressed as well: women are naturally monogamous and suffer jealousy and envy much more painfully than men. I think gender-based opinions like this are dangerous. People are people.