The computer analysis has a little problem...

As people have said before, it wasn't a big enough loss.
As for #3, there's the infinite analysis option, and if you want more firepower, I'd recommend actually installing the stockfish engine directly, and getting a good Chess GUI. (I'd recommend Arena)

The engine should point out every imprecise moves? That's probably 90% of moves per game.
Also, let's say the engine likes 1.e4 .
Should 1.d4 be marked as imperfect then just because it might be 0.05 weaker according to the engine? Also engines also have a play style just like humans so the engine would critizise every move that doesn't fit it's play style. Doesn't make much sense.

Ok, I got it. Thanks anyway :)