Well, reading your thoughtful post completely a couple times, it brings to mind a couple thoughts and concepts.
I know I and others have commented on these in the past - at least in a general way.
1> The concept of "the other half", "singular soulmate", "completion of our-SELVES" etc
2> The concept of what seems to be commonly referred to these days as "synchronicity"
1. Myself, from observing and thinking for many years, I cannot feel any other way than that this 'quest' so many seem to be on for this 'other' part of them-SELVES is a false and unattainable quest for most people. The concept that we need to discover our true "selves" and that other people may play a part in that I believe IS valid. But humans are multifaceted beings and collecting those pieces seems to require a lot of different sources. Not speaking here even of only 'people'.
From reading your writing, it seems to me that there's a part of you that already understands this. So it's highlighted the conflict with what you know inside. That knowledge does NOT seem to be present in your partner. Yet.
One this note, I also think that everyone is unique and different and that some people, maybe because of (karma?), life circumstances etc, have had their 'pieces' more scattered and will have to broaden their lives to recollect them. It's been spoken of here about the concept of "fullness" which I define as that point we reach when we feel complete - that it seems we've collected all that was hidden or lost to us. And I think those needs are just simpler for some people. They reach that state almost effortlessly.
So I think that this whole concept of "other half" can be a dangerous illusion for a majority of people and a common cause of a lot of heartbreak in the world.
2. There is this concept that's becoming more well know these days I think (not new - only more visible) that we attract what we 'need' into our lives. Most times without even searching for it (consciously). When it comes to "people", I feel that these attractions are very much of a reciprocal nature. People come into our lives because they are carriers of some wisdom WE need, but in most cases it also seems they we have something THEY need. Sometimes this wisdom or knowledge - this "piece" is not real obvious at first. But I think if everyone was aware of this dynamic and would take the time to just sit back and ask the question "Why", or at least be open to that, it will often shed light on the connection and may even expose that it was not at all what we first "assumed". Sometimes we go fishing for bass and catch a tuna !
Hope that makes some sense ?
So I guess what I'm trying to say is that it may be most beneficial for you both to just "flow" with it. Try not to force rigid frameworks around it or fit it into preconceived "boxes". When we look back years from now we often see things that we've "broken", and therefore lost the value of, because we insisted on fitting them into a space that they just wouldn't go.
Hope this helps............