How to open log files

There is not.

Yes, it would be very difficult to do and requires stopping and opening the IoTaWatt. The log file is in binary form and is a unique format.

The new query will support exporting a modest size CSV file. The major hurdle with getting this out is user interface. It’s a substantial JavaScript effort and browser compatibility with things like date/time specification is an obstacle. That’s also holding up a revised new graphing capability.

Even if you don’t have internet, it is advisable to be connected to a WiFi network. That being the case, you can run influxDB or EmonCMS on a RPi for short money and harvest the data that way.