Now I have installed Rockpool beta, and even received one incoming call ! Actually, it went well, the watch didn't boot, nor did the phone freeze.

But the bluetooth connectivity issue is still there: I tend to turn bluetooth off from the phone for night time. In the morning I turn it on again, and the phone and the watch find each other perfectly every time, but Rockpoold does not notice the connection until I restart it.

EDIT: Another succesful call !! \o/