Welcome to the forum, Alan. I think the missing field for token count is a bug that has been reported on multiple occasions, like here Why is token_count in GenerateContentResponse always 0?
There is a potential workaround, by using the usageMetadata field, as described in this post:
The field is documented here: GenerateContentResponse | Google AI for Developers | Google for Developers
I have been unable to solicit official guidance from anyone in Google whether the workaround is expected to become the permanent fix or whether the per-Candidate token count will be eventually introduced into the implementation, aligning the implementation with the documented API.
Hope that helps