Bended ballscrews. What i can do?

[magicniner]

I put them on v-blocks and tried to apply force in the middle.

For straightening you ideally need to apply a precise displacement then measure to see if you have achieved a permanent change, then keep increasing the displacement applied until you get the required change.
Measuring force is an imprecise way of straightening things, a press with a dial gauge is your friend ;-)

- Nick