At this point I am simply going to try crafting a manual bitcoin transaction using a private key derived from the 24-word seed phrase and see if when submitted the bitcoin network will move the coins for me.
Wait a minute. You said that the coins were visible in an address when you imported it into a watch-only Electrum wallet. So why don't you try playing around with the derivation path on both seeds to change it to ones that could be probable Trezor paths? It's basically the first 3 numbers you need to manipulate. It goes down to the second and third numbers if you know the address prefix which you seem to know: Paths start with 44, 49 and 84 (I believe they are all hardened) for 1, 3 and bc1 addresses respectively.