Hi, this asset pack can be used for any type of project including commercial without any limitation, credits can be offered if deemed appropriate, but it is not mandatory.
As for the attack animation, the fact that the weapon sprites and the effects are separate makes the possibilities are many, it is a matter of creativity and what the game engine offers you. I show you a simple example but it could work well, the weapon sprite is rotated backwards to create an anticipation, in the next frame the weapon sprite is replaced by the hit effect sprite, at the end of the hit animation it is replaced again by the weapon rotated forward, and would end with the starting position. You could even add movement to the character's body to further exaggerate the impact, something basic but effective. But even more could be done by simply rotating, squashing, or stretching the sprites.
If you are interested in discussing it further I could give you some more ideas, in my portal you will find my email address and my discord id in case you want to contact.