This is an odd coincidence, I just received an email today from one of my users (I run a Pinboard "competitor", https://historio.us) that mentioned the same problems, namely emails having gone without response and an inability to get their data out.

I'm afraid I can't answer your first question, but I can answer your second one. historious has been around since 2009 and, while I don't give it amazing amounts of love, it works well enough that I use it myself. I am currently trying to modernize it a bit, but I don't have an ETA or roadmap on that. However, I think it's worth giving it a shot.