That means that each single key may correspond roughly to 2256 / 2160 = 296 addresses, right?
No, it's straight up 2^160 addresses, no need to divide. RIPEMD-160 is used to hash the SHA-256 hash of the corresponding public key [1], reducing the P2PKH address space from a potential 2^256* to 2^160.
*slightly smaller, ECDA's private key space does not cover the full 2^256 [2]
So in fact addresses are not unique in their nature cuz bunches of them have the same private keys.
There's also P2SH and Bech32 Bitcoin addresses, so any private key corresponds to at least 3 valid Bitcoin addresses.
[1]
https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses[2]
https://en.bitcoin.it/wiki/Private_key