would it be theoretically possible to ascend twice? firs you kill your dreamself on the slab as your waking self, then you kill yourself on it, does that leave two god versions of yourself?

If Aradia’s Ascension is anything to go by, if your Dreamself Ascends, your normal Self dies. Even if it didn’t die, whatever happens to your Original Body, it stops counting as your Main Body- Ascension makes the Ascended self your ‘main’ self, and your ‘main’ self is the one who has to die on the Quest Bed, which would make it impossible for you to ascend a second time. That is if Paradox Space even allowed the circumstance of you and your Dream Self actually being in the Moon and allowed to ascend normally, fate likes to pull some pretty rough stuff at times.