I would like to ask you a paricular question. Recently I had a job interview which, as far as I am concerned, went great. However, I might have made a stupid mistake and I would like you to tell me whether it sounds awkward or not. So, in the final stage of the interview I was asking questions myself. After the last question I said something like: "That's all, thank you very much." I wanted to thank the interviewers for answering my questions, but I didn't add this detail. Now I think that it might have sounded bizzare, as if I was the one who conducted the interview and wanted to finish it. What do you think?
if you said "That's all, thank you very much." after the interviewers had answered all of your questions, then the "thank you very much" would be taken by them to indicate gratitude for the answers, and no more would be required, and omitting to say e.g. "...and thank you for answering my questions" would probably not even be noticed. Anyhow, the only answers you are going to get here will be opinion based and thus off-topic.
There's a nuanced difference between That's all and, say, That's all I had. The latter can have a tinge of deference and the former can have a tinge of command, as if you were running the interview.
But a deferential tone of voice and body language would probably counter the latter effect, and even if it didn't, some interviewers would appreciate the fact that it's a two-way meeting, where the candidate wants to learn about the organization just as much as the organization wants to learn about the candidate.