a few vocabulary/grammar questions

Would someone be so kind please as to answer my questions?

Is muffin texture what to say?
They sell this chocolate chip cookie with a muffin texture.

Is wear off correct?
The caffeine is wearing off.

Is wave correct?
If I get over the wave of being tired, I can go another hour. I am tired by waves.

I couldn't find impactful in the dictionary, is that correct?
It's more impactful if you call than your parents.

Is this natural? Is behalf correct?
The person I am calling on behalf of is John.

Which word is correct?
Tie the boat to shore/pier before letting people off.

Thank you for your time