OSX has had FileVault enabled by default since 2014, though we don't know how old the laptop in question actually is.

It's not hacking to decrypt your own data. The argument is, and the precedent set by law supports, that failure to pay for and retrieve the device after a set period of time transfers ownership. It's basically the legal grounds of "finders keepers"

People keep asserting that ownership of the data passed to the shop owner, but it's not at all clear that's the case.

1) Assuming Biden did bring and abandon the laptop, what do state laws generally say about data ownership? What does Delaware law say about it?

2) We can't assume it was Biden who brought the laptop. Suppose it was stolen: naively, I'd guess ownership can't pass to the store owner, because the person who brought it didn't own it in the first place. But who knows: IANAL. What if the laptop was legitimately owned by someone not Biden, but they stole Biden's data and moved it to the laptop before abandoning it?

3) Again naively, it appears that the shop owner definitely and Giuliani potentially distributed intimate videos of Hunter Biden without his consent. That would seem to run afoul of revenge porn laws, which are on the books in both Delaware (as of 2014) and New York (as of July 2019).

I don't know if the blanket assertions you're making are accurate or useful. At the very least, they need to be fleshed out, and there's way too little information available right now to say conclusively that the owner of the shop broke no laws.

That would still violate the DMCA where owning data isn't important.