< > Downplay your own role. You're Cirucci's Fraccion and lover, who was with her before she reclaimed the seat of the Diez, let alone the Quinta. You only managed to do as you did due to the memory glove you're wearing, along with your bracelet and the reiatsu hiding king's cloak you no longer bear. You'll be less important seeming, less valuable, but also less of a threat. You'll also certainly be stripped of your remaining Marana items, even if you can play off the reason for giving you so many being that most Arrancar can only use one at a time, and you four.
< > Hide your Marana items. You can easily mention your abilities from the items without mentioning them themselves. He already knows about the memory glove's powers, but not where they come from. He also already noticed your necklace, but if he examines it, he should see that it would be difficult for most to attune themselves to more than one such object. You'll be painting yourself as a more powerful natural Arrancar, but with powers that don't change so much. A threat, but a known one, and with the option of maybe making a new item to give you an advantage for later.
< > Come fully clean. It'll be giving up all of the information without a fight, but your abilities with La Marana already gave you the respect of one mad scientist, and might get the same from another. You're valuable for those abilities, which is all the more reason for him to believe that your side would be willing to consider your safety in negotiations as the shinigami will consider Ichigo's. And, if you're able to barter your services to them, you might be able to earn a better position to work things towards some measure of true diplomacy rather than just going through with Lord Aizen's plan as it is. At least with these Exiles, even if not Soul Society itself.