battery bugs and questions

Hi,

I have some questions / bug reports / feature requests about my Mk2i's battery management - 

1. After charging it to 100% (or close to 100%, e.g. today I unplugged it at @96% if that matters... Anyway I try not to leave it connected once it reached 100%), it prompts me to "turn on battery saver" because "the battery is too low". It may have been too low before I charged it, but now it's (almost) full... How can I stop that behavior?
2. At full charge and without any diving, it lasts about 4 days, which feels extremely low compared to the promised 16 days (with 24/7 HRM) and to the watch's own prediction of 8 days...
   1. How can I see what's draining my battery so I can stop it?
   2. Is the estimate a software bug, or am I doing something wrong?
3. How should I charge the watch? Someone told me to keep the battery between 20%-80%, but that doesn't sound right... Is there any official advice on this?
4. Can I see the battery percentage on my phone? I'd like to have my phone alert me on certain levels (using something like IFTTT or MacroDroid)

Thanks in advance to all those willing to try and help :)