That doesn't look to well, but then again, I could post logs from my boiler module with similar recordings. In other words: I don't think it automatically means your module is a goner.
The unknown first byte is part of the bootstrap of the module:
Toon sends 128 'j' characters first, and then starts the actual initialization. This can take quite a while. I have logs with exactly the same content, including errors, recorded from a working boiler module. At some point I had to repeat the test for opentherm capability more than 10 times before it worked. Don't ask why, because I don't know

.
How is the connection between
toon and the module? If you just connect
toon and the module, and forget about the boiler for now, does that work (two short pieces of wire, between
toon and the module, and test e.g., on your kitchen table)? Naturally, you will only get bang-bang control, because there no boiler to respond to
toon's requests.
grtz,
marcelr