Following the Trezor guide won't help you since your funds were not on the BTC addresses controlled by the Trezor private keys before August 1st (right?). They are on the many addresses you mentioned.
- Send all your bitcoin to your Trezor but keep track of each address that had BTC prior to the August 1st fork.
- Next, import the private keys for those addresses into Electron and you'll see your Bitcoin Cash show up there.
- Send that Bitcoin Cash where ever you plan to store it securely (not sure how Trezor supports Bitcoin Cash, but my Ledger Nano S does).
Also keep in mind you may have Bitcoin Gold or Bitcoin Dimond (and who knows what else) on those addresses as well. Good luck. As long as you always have your private keys (and backups of your private keys) you can't mess up too badly since you can always start over again if you get stuck.