I know you guys refuse to hear it and keep ignoring it, pretending that I never said that. Therefore, I want to repeat it loud and clear once again:
No, my husband did not just make it up to keep me (having a plan of never executing it on the back of his mind). This is just not the case. Just like me, he is honest to the extreme of it and he just never does such things. He took a model of a quad in his book as a model of an IDEAL union BEFORE it even came up between him and me. He kept going on and on for days afterwards starting conversations about a quad, going through different endless possibilities this union is opening up and wondering how come many more people do not come up with this idea. He very much wanted and asked me to call together my neices (they are 19) to share with them this exciting idea, because he was excited to NO END. When he offered the quad idea (and days afterwards) he MEANT it, I am absolutely sure about that. I know my husband, he does not play games, he does not lie. It was a very honest proposal that he was very excited about. He 100% meant it.
You can rehash the whole "but it was his idea" and "he said maybe one day in the right circumstances" all you like but, right here, right now, he doesn't want to so either you respect that and look at other ways to improve your relationship or it's a dealbreaker for you and you separate and find a quad of your own.
Sorry if that sounds harsh but I really don't see any other options at this stage.