To let someone go

To let someone go
 

How would you translate <let go> in each of these examples?

His parents didn't let him go to the zoo.
It's getting late, I better let you go. (on the phone)
She was a good friend, why did you let her go?
I need you. I'll never let you go.
Hold on to the rope and don't let go.

The first four can be translated with "dejar ir". The first could also use "permitir ir". The last would use "soltar".

Another use would be "to let someone go" as in firing them, which would be translated as "correr" or "despedir".

His parents didn't let him go to the zoo.
Sus papás no le permitieron/dejaron ir al zoológico.

It's getting late, I better let you go. (on the phone)
Ya se está haciendo tarde, mejor te dejo (ir). (hablando por teléfono)

She was a good friend, why did you let her go?
Ella era buena amiga, ¿por qué la dejaste/permitiste ir?

I need you. I'll never let you go.
Te necesito. Nunca te dejaré ir. (Nunca dejaré que te vayas)

Hold on to the rope and don't let go.
Agarra bien el lazo y no lo sueltes.