Hi,
Paul again here 
Second impressions:
- I de-installed Nova Launcher - the crashes stopped !! I reinstalled it, and the crashes came back. So, for the moment, I would advise people not to use this Launcher on the FP2. (I do use quite a bit of apps, so the FP2 launcher is not really workable for me. At the moment, I am using ZenUI. I do not like all those “extra launchers”, but I need more space than just one homescreen. )
- About the failing proximity sensor: if I am using a headset when the phone rings, I need to take it out as I do not yet have a headset with a working mic. When I then raise the phone to my ear, the proximity sensor does not shut down the screen. So, I would as people to test this scenario, but for the moment this would seem a bug to me: the proximitysensor is not re-engagaged when you take out a headset plug and use the phone in “normal” mode.
So, working with it, for the moment the FP2 for me is a workable phone. I will try some other launchers, and am searching for a good headset to use with it. I am aware of the wiki, but I want an “sports-in-ear”, like this one. But at the moment I am hesistating to buy it, not being sure if it will work
Regards,
Paul