- It weights about 400g including the wooden stand.

- It draws very little power. I am not sure how much, but you can run it on a battery pack for quite a while. (The power draw is so low that some external battery packs think that nothing is connected and go into standby, which is annoying.)

- Yes it uses WiFI. Not sure about WPA3 to be honest.

- Private iCloud calendars should work if you get the secret iCalendar URL as described in the article you linked.

- There is very little processing on-device, it needs an API backend that runs on the internet. Code that runs on an embedded device and updates only via Over-The-Air updates is always a liability in terms of maintenance and security, which I tried to minimise.

- The device polls for updates a few times a minute. But depending on the calendar integration, there may be caching going on in the backend. (For example, iCalendar data is cached for 10 minutes. The cache is encrypted.)

- Yes, you can combine calendars from multiple sources and accounts.

- You can replace the frame if you are willing to tinker a bit, re-solder a connection, and are you're careful.