Unfortunately, no it doesn't store the metronome setting, and always reverts when you go out of the function. I would love for it to persist but I suppose that would have some memory implication on an already extremely modestly provisioned device (it's kind of amazing what little resource Infinitime uses as an RTOS).

the long press on watch face will only work on specific designs; I use the Casio style one, which doesn't offer any customisation options, but others like Infinibeat and Pride Flag do 😊

and absolutely! I always keep an eye out for new versions, if only to read about the trials and tribulations when developing for iot devices.