Really, really interesting post.
I can completely empathize and sympathize with you. Having faced much of the same derailing....women just don't want to share...I have not faced really any severe aversions to married versus a committed relationship but that's not to say that even the committed relationship aspect of the conversation ends up a deal breaker.
Ultimately it comes down to finding some who can see marriage as a committed relationship that is on the next level.
I cannot give insight into the women who reject us and their mindset other than what I have been told and it comes down to married or just in a committed relationship the reasons are the same.
As for your SO feeling like it's her fault, you'd have to ask TP about that. She has expressed to me that it's not me that they are rejecting but her.
Polyamory is wrong! It's Multiamory or Polyphilia. Mixing Greek and Latin roots? That's wrong.