"Q1. Is it ever morally acceptable for an adult to have sex with a pre-pubescent child in modern western cultures?"

No. Even if you accept the theory that sex in itself is rarely harmful, the consequences of police investigations and legal proceedings would be likely to cause trauma.

"Q2. Would having sex with a pre-pubescent child be morally acceptable if the culture were different?"

I'm undecided. Culture may well play a large part in whether such an act is likely to have negative consequences on a child. Whether or not it was a cultural norm, my view would be determined on the basis of empirical evidence.

"Q3. Is having sex with a pre-pubescent child in modern western culture spiritually accetable?"

I'm undecided. I don't hold spiritual beliefs. It's up to individuals who hold such beliefs to decide if such an act is in accordance with them.

"Q4. Would having sex with a pre-pubescent child be spiritually acceptable if the culture were different?"

I'm undecided. Reasons are stated in my previous answer.