You have three separate aspects of yourself, and they are all at odds. There is your logical self that can see the benefits of transcending insecurity and jealousy. There is your emotional self that has been conditioned to monogamy, and then the aspect you touched on only briefly - your underlying beliefs. I would suggest focusing on determining exactly what you believe. Beliefs can change when presented with new information that we didn't have before, but it is messy at best and impossible at worst when we don't know what our starting beliefs are.
Get down to basics.
1. Do you believe polyamory is wrong?
2. Do you believe you don't deserve to be loved?
3. Do you believe that love is finite?
4. Do you believe you are less of a person if you are not one half of a couple?
(These are just examples - you may have others that are more appropriate to your circumstance.) Once you determine what your beliefs are, next ask yourself why you have them. All of us often hold the default societal view - until it is challenged. The challenge makes us uncomfortable. But examine what the belief is based on. Is it simply what you were taught? Or does it logically make sense?
Additionally, a lot of the strain of polyamory is that it hits up against the thought patterns, the labels by which we identify ourselves. "Hi, I am Mr. So & So, Jane's husband (or SO or bf). While that may very well be true, it does not have the same exact meaning in polyamory as it does in monogamy - which implies sexual exclusivity. I think of myself as one individual who loves another individual - not as part of a couple.
I know the process feels like hell. I am sorry you are feeling so off-balance. But your tectonic plate analogy is a good one. Your underlying belief systems are being challenged. And while your emotions are screaming to let those plates slide back into place, your logic is not permitting it.
I know your love for this woman is what started you down this path, but even if you walked away now, you have questions that require answers.