About your questions:
1) Fathom, Simple Analytics, and Plausible are great. They have done an incredible work too. Panelbear has already most (if not all) of the features you might find in their offerings. However, I do intend to dive into more advanced functionality, while keeping it simple to use. I will be talking more about it when I feel confident about what I can deliver.
2) I launched in September, but only with a few posts here and here. It was also a lot more barebones back then. I try to release a new feature each week, and traffic has been slowly ramping up. I guess I just haven't had much time to promote it, but I plan to keep writing blog posts if there's something interesting.
3) I try to limit work on Panelbear to 2 hours per day. If I want to be in this for the long-term, it's gotta be sustainable, and fun. I try to leverage most of the tools I already know, even if unconventional like Kubernetes, to help me focus on shipping rather than learning a new tool.
Glad you like the design :) I took courses in design when I was studying, but I actually struggle a lot with it. It has helped me appreciate just how much work goes into a good design.
Thanks!