All goons are playing the animation for you're not picking the specific instance. The goon isn't referenced in the event, just the goonbox.
This can probably be fixed by using a container and putting goon and goonbox in it. that way they are related at all times.
AI is a difficult subject, because everyone wants something different. You could for instance do a for each check and a system compare distance(player.x,player.y,ggonbox.x,goonbox.y) < (a certain distance) and have the goon attack when that's true.
You could use pin for the monkey, or set position. pin would probably work best here. Just make sure to pin the hand of the monkey to the bottom of the rope location only.