“Since when do we pasken according to kabbala?”
Since the kaboloh was revealed. Kaboloh is an integral part of Torah sheb’al peh, and denying it is kefirah. And yes, the Ari Zal, whom klal yisroel has accepted as a definitive posek whose torah came directly from Eliyohu Haovi, paskened that interleaving the fingers is forbidden.