In many US states, even a verbal contract is legally binding. Obviously this depends on many factors, the terms have to be reasonable and it has to be clearly communicated (and it's generally harder to prove a verbal contract in court). Text and email communications are the same way.
In your example, it likely wouldn't be considered a valid contract though. The terms have to be reasonable for both parties and there has to be a clear understanding that it is an agreement. Getting "ok" back is presumably sarcastic or not genuine.
I've never had one that required an interview, but my primary private tracker requires you to log into the webpage not on a VPN. They still suggest heavily that any torrenting is done on a VPN though.
If the owners of the site are competent, they're gonna hash your IP for their logs and not store the actual IP. Hashing is a one-way process, they won't be able to reconstruct your IP from it. If they're storing your raw IP, probably stay away. (Honestly, you can't do nearly as much damage with an IP address as people think, but it'd be a hint to way worse security practices elsewhere)