No, the second you connect with a person on the same server you end up having it changed due to them not having you on the trust list.
I'm not so sure. I have multiple blockland files for different computers, and I often will see someone that I don't have trust with on that copy, but I have trust with on my other one, and they don't lose my trust when I go back to my other one.
I think it is simply that it checks both people's results, and if they both say yes, then it is a yes, but if one of them says no, thats not my friend, then they don't have trust.