1) Mac address: neither the ENC28J60 nor W5500 chip has hardware MAC, so yes it needs to be software defined. The Mac is derived from ESP8266’s Mac, with only the last byte differing from each other:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/blob/master/OpenSprinkler.cpp#L442
so it’s not totally made up from nowhere, but it’s based on the true Mac of ESP8266.
2) Configurations: the firmware only triggers a factory reset if upgrading across major revisions (like from 2.1.9 to 2.2.0). Within the same major revision, the configurations are preserved, because flash structure and all file formats are the same within the same major revision so there is no need to reset flash.
3) John reported issues when the configuration is large (i.e. large number of programs and/or zones). I haven’t had time to look at it yet but will import some large configuration file to check. Meantime, if you can see the homepage that means it’s fine. I would suggest not adding more programs or zones until I figure out the issue.