There is one thing though that puzzles me a bit: using my 12-word wallet-recovery phrase in the BIP39 phrase generator, I cannot find the change address. I'm wondering if it is just buried thousands of addresses down or if the wallet uses another phrase. I'd prefer to have the private keys of all my addresses in the wallet, and right now I do not have that, and the change address is the one with the most money in it.
Receive and Change addresses exist on two separate "paths" in an HD wallet using BIP44... They are more correctly known as "External" and "Internal". External being the receive addresses which are used for sending and receiving coins from external sources... and Internal are the change addresses which should only ever be used internally by the wallet for catching change amounts from transactions.
On the BIP39 Mnemonic Code Convertor (
https://iancoleman.github.io/bip39/ - use offline copy etc)... if you put your 12 word recovery phrase in... by default it will use BIP44 with the derivation path m/44'/0'/0'/
0, that shows "External" (aka Receive) addresses... set the External/Internal value to 1 (derivation path: m/44'/0'/0'/
1) and you will get "Internal" (aka Change addresses)