Your intuition is telling you there is something weird going on between her and ex, correct? From what you disclosed, it was pretty weird for years before you came along.
Why should now be any different?

Any relationship where people are in still in contact with previous partners is a source of anxiety. This is not an issue unique to you. Your situation may seem mild to me, but to you it is a potential deal breaker. Am i right about this?

I sense a great amount of conflict. The "logical" side wants to be with her. Your intuition wants to be free, because you feel in your gut, uneasy. You cannot abide the ambivalence.

You obviously have a high level of education, based upon the structure and content of your posts. However, have you ever considered that focusing on the minutia has distracted you from the bigger picture? Have you ever heard the phrase "analysis becomes paralysis"?. Do you want a life with her? Then you must.....

TALK TO HER

Keep it simple. Speak from the heart and don't be attached to the result.

As for myself, yes , i lived with a narcissist for several years. So i know what it is like to be "lost". To have your whole identity erased, all to keep from being alone.

When you ended it with your ex, did you listen to your head or your gut?