With the movement manueouvre "Adjust speed", it`s posible to reduce the ships speed to 0? Effectively not advancing more than 10k KM and then turn?

yes

You need to get a lot of Degrees of Success if you aren't driving a slow ship, but yeah, with sufficient DoS, you can rotate in place.

There really should have been a bit more granularity in the 'base' speed/movement options to start with, say full speed, half speed, full stop, and then need to more finely adjust from there.

Just make your own 1/4 speed, cruising speed, 3/4 speed, all ahead full, and flank speed colums for each ship and limit how many categories you can change in a single turn.