It started last night,...
These things do sound "mostly" normal...
The shut-off has happened to many of us, thankfully it's gone away.
Switching it on and off generally resolves it, but HD/LW has not identified why yet.
it will click when turned on in any way, as it's using the battery to do something.
the % will fluctuate as you ride, showing more or less based on speed ridden, etc.
Many times I am low and know I can make it, even if it says I might not, by adjusting my riding/speed.
There is a display item "widget" on the right/left that shows the lowest range (likely if you ride the fastest), its middle (average based on how you have been riding) and the longest range if you ride more cautiously.
hope some of those notes help with learning your ride!
If service gives you deets, we'd love to hear them!