But if you insist on sticking with paper then the paper needs additional protection such as a hard plastic laminate that can make the paper more resistant and use storage that has strong durability, such as a time capsule made of strong and sturdy stainless steel material and can be stored in the ground or wherever you want.
Regarding this stainless steel capsule, I think the capsules sailors use to store medicine, for example, could work, as some are made of stainless steel and, above all, waterproof. They don't cost much. However, in the event of a fire, I suspect the paper inside will burn, unless the capsule is buried deep in a garden. Unless, perhaps, you place several capsules inside each other like Russian dolls (matryoshka).
But what would be interesting to check first and foremost is how you created your wallet in the first place. Imagine if your wallet was emptied after several years because you created it online on a dubious website?