How did you do the online booking with LAN? Could you kindly ket us know the URL and what limitations you found?

Your original question about AA status seems to have got submerged a little along the way. It would seem sensible to gain OW Sapphire status before setting out on a trip like this, especially as the bulk of the distance to be covered is going to be done in one hit. You might take a look at the AA forum for advice on recommended ways to Platinum. I've heard of something called the Platinum Challenge; maybe this would be a good thing for you. Us BAers have enough pain with our own system that I at least don't retain the intricate details of AA, I'm afraid.