I can't reply to all of your questions, and I'm afraid that nobody can. But obviously all functions aren't not yet working in the Sailfish port. And, as you might already know, proprietary functions, like Android app support for example, are not included to unofficial ports. So one could say that "all functions" aren't even going to be available, at least if Jolla won't decide to make official version of Sailfish for the Pro1. But if I haven't mistaken, the Sailfish port for the Pro1 is in Alpha stage right now, so the porters probably haven't been too worried about things like battery life.

I'm personally going with Android at least in the beginning. I got frustrated to Sailfish while using Jolla phone/Jolla C/Oneplus X w/ Sailfish port. So for me Sailfish on the Pro1 is not a must, but of course it would be great thing to happen. Personally I'd rather see Maemo-Leste or some other proper Linux distro on the Pro1, along with multiboot ability. But right now everything I hope for is that they manage to actually publish and produce the Pro1 and they find enough customers to succeed.