I don't know what you mean by "If I could play Al Pacino's butt". Do you mean there's a part where you play Al Pacino as a character? Or do you mean that now you have a foot in the door, you might have the chance to play up to him ("play his butt" sounds quite dodgy)? Or do you mean that by acting opposite Mr Pacino, you could impress him?
Anyway...
1. Because "could" is actually a past form of "can", keep it consistent with the second conditional. I'm sure you know the rules. ;) Using "will" sounds wrong because you're deducing a strong possibility (will) out of a weak possibility (could).
"If I could play Al Pacino's butt, I would have my actor's dream realised." (or "acting dream")
2. "Would have" is in third conditional. This means it never happened; the chance is lost.
"If I had played Al Pacino's butt, I would have had my actor's dream realised."
3. I'm fully in agreement with Katya here. It's all unreal, so it's subjunctive mood anyway. By "unreal", that means it doesn't happen, or hasn't happened, in reality.
* "My agent has just got me a job in the new Al Pacino movie!" - yes, this is real. it happened.
* "If I could play Al Pacino's butt..." - this is not real. You're imagining a possibility. (I still don't know what you mean, so maybe this is a good thing.)
* "I would have my actor's dream realised." - this is an imagined situation based on... an imagined situation. :) It cannot possibly be real.
Sorry for the lengthy answer; hope that's clear enough.