Several things come to mind from your long description
you are full on attached, in love and have an unhealthy dependency on the relationship and maybe her. Wow.. you would do surgery.. she is that vain that you think only height plays a part in her decision?.. honestly either she sucks as a person or you don't trust her decisions.
You are pushing pushing pushing, and she is holding you back. Desperation is never attractive to anyone, and it sounds like she is being honest, but also trying not to hurt you. At the same time when you step back it sounds like she is still holding onto the strings. Emotional abuse all around. She needs to let go and so do you.. or she needs to stop being so nice and just break up with you 100%.. (or visa versa)
My advice.. is to walk away. It doesn't sound like she wants to be open, it doesn't read like shes into you as a lover (based on your expecations vs what she wants) and its LD to boot. It just doesn't seem like you guys meet on any level beyond past history.
Not to mention being in an open relationship with the "downgraded" pov about relationships becomes really tough.
She is young.. she is blossoming.. she is discovering.. you are in two very different places with two very different perspectives on life and two very different expectations.
Predictably, I'm also scared that I won't ever meet another woman to really like and fall in love with, given that I'll never, for the life of me, make the mistake again of dating women even close to my height (this is not the first time I got burned because of my short stature), which drastically reduces my dating options. I also live in a suburban area that's not friendly to singles, my business isn't going well at all, and generally I'm in a pretty bad place in my life.
sooooooo Ya.. I have been here and you really need to just have faith. Sounds like hooey when someone is saying it, but its true. All the cliches are reasonably true.. more fish, things get better etc.. but in your current state it will seem like bullshit.
You need to step away from the chaos you are creating.. a few weeks and you will start to feel a bit better, keep analyzing and look at it from other eyes.. opening the relationship is far from a solution..
When I say step away.. I mean cut the cord, tell her not to call and take time to yourself.. I am empathizing.. I really am.. but the solution you want.. doesn't read like its going to happen