Thanks to the OP for the update, and glad to hear you are at least getting closer together. Hoping for a crew that’s willing to perhaps to help it all work out in the end. Obviously and you know this, just keep calm, be polite, but do be willing to point out that you had made a point of selecting seats together way back when you booked this. Whether you actually paid for seating is somewhat beside the point, since you’d have also been able to book another carrier, but chose to book oneworld for, among other things, being able to book your seats.

If it’s a short holiday together, then I don’t feel being separated for a day of it is a small matter, and I’d be upset if I were in that situation. Sounds like you have at least for now cleared that hurdle. I don’t know how many seats there are in the Club cabin compared to the 8 in F on my flight, where a bit of seat shuffling was quite simple, but hopefully something agreeable can be worked out. From the sort of route that this one is, though, I’d expect a lot of people travelling in couples or families, so could be harder to find a solo traveller such as myself who is happy to move. And if there are people who’ve also paid for seating rather than having via oneworld status, even more tricky.

Best of luck. You sound like you’ve put a lot of effort into this, and it will be all the more nice if you get a good outcome.