How could I damage entities in certain distance/radius from the player with a low amount of damage

So I'm trying to create a spell mod in 1.15.2 that will do potion effects and damage to surrounding entities on a right click of the item.

I've tried " /effect give @e[distance=..6,type=!minecraft:player] minecraft:instant_damage 1 1 " but that does way too much damage than id like.

Also how could I knockback all surrounding entities.

I also really don't want to resort to using poison