Re: how long to push
I don't know how long, sorry I can't help answer that question for you. But I have a slightly similar concern, sort of. When my DH was a baby, he was over 10 lbs. and his shoulders too were so large, that he actually broke his collar bone as he came out the birth canal. Basically, the Dr.'s wanted to do a c-section (at some point, not sure what point during MIL's labor) and the stupid dad said "no way are you cutting open my wife" - rumor says he didn't want her to have an ugly scar - real winner, huh?).
Now days they would NEVER do that based on what the man says - I think I've heard it's all about the woman's ability to decide what happens to her body, and the man only has a say so if the woman is knocked out or something.
Anyway - if I have a big baby like my DH was, they may have to do something similar. Hopefully all goes well with your delivery!!!