In a hypothetical situation, in reference to brutality(Darth Vader/Royal Guard Champion)/multi-fire(Sentry Droid), if i were to use the first action to gain movements points, and i were to use either brutality or multi-fire, since it says to attack another target, can i interrupt between my first and second attack to move? or do i have to stay in the same spot and attack two targets?

I feel like it is broken if you can do move in between two attacks.

Spending movement points is a during-your-activation ability, and you can't use those inside actions (or other abilities), only before or after actions.

The FAQ goes as far as confirm that they are not interrupting abilities.

TheConsolidatedImperialAssaultRules said:

An ability that can be used "during your activation" (p.28) can be used before or after performing an action during an activation. Abilities that can be used "during your activation" are not interrupting abilities unless otherwise specified, and thus cannot be used while resolving another ability.

RRG said:

An ability that can be used “during your activation” can be used before or after performing an action during an activation. It cannot be used while resolving an action.

FAQ said:

Abilities that can be used “during your activation” are not interrupting abilities unless otherwise specified.