The character models are saved under .tfa and I can't figure out how to open them. I assume it's a custom file format.
I'm not trying to pretend to be some kind of programmer god, but on the assumption that you're a novice programmer, I'd suggest you don't assume. Measure, and try the most obvious things.
For instance, why would it be a custom format? I would be sceptical that anyone would waste time writing a custom datatype that can do everything Unity can but better.
Even money it's a renamed Unity asset format, and if so, you could simply change the file ending and attempt to load it. It may also be a zipped archive; here, again, it's just a matter of renaming and extracting, just like you'd do with an EPub or ISO file.
...just for kicks, I opened the 2b file in Notepad++. It's parts binary, but it's got a nice little file signature, which indeed reads "UnityFS."
First google result leads
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. Go nuts.