Obviously you can create multiple wallet addresses with one Trezor hardware wallet and just one seed phrase.
That's correct.
However, I don't know if one seed phrase has more than one BTC address...
It's the same as you said previously. In Trezor, your create a Bitcoin account and there you get your first address. After you fund it (optional) you can generate a 2nd, 3rd, 4th, and so on.
if our Trezor hardware wallet has problems such as a dead screen or other problems, other BTC wallet addresses (not the main wallet in Trezor) can be accessed in other BIP39 wallets or not.
You can access all your BTC in all the accounts you created in Trezor at the different derivation paths if you point your Electrum software to the correct account (derivation path). It doesn't matter if it's your main account, as you call it, or any of the other accounts. Their difference is in the derivation paths. If it's a native segwit account, the derivation path for the first BTC account should be m/84'/0'/0'. If you created a 2nd account, it's at m/84'/0'/1', etc.
In my experience
https://bitcointalk.org/index.php?topic=5467802.0, I have 4 BTC wallet addresses in one trezzor with one seed phrase, because there was a problem with my trezor, I was forced to access it in the BIP39 wallet (I use a trust wallet here) where only my main BTC address appeared.
You have greatly decreased the security of your seed phrase. Generate a new one on Trezor or offline, and move your coins there.