How long should I breastfeed on each breast?

Yes. Depends on how fast your baby sucks and how fast your let down is. Some babies will suck and finish a breast in 10 min, others will take 20. It is not necessary to feed on both sides. As your supply increases you may only need to feed one side for each feeding, just make sure you alternate each time to keep up your supply on both breasts.
Yes. Feeding 5-10 minutes on each breast is fine.
Yes. Feed on the first side 15-20 minutes, or longer if baby is still actively suckling and swallowing. Feed on the other side until baby seems satisfied. Some women with quick let-down may feed faster, but more often babies that don't feed long enough on each side get foremilk/hindmilk imbalance which may cause increased gassiness, green stools, colic symptoms, spitting up, and frequent hunger....
Yes. Generally 15-20 minutes per side is sufficient to drain most of the milk. Babies who nurse much longer generally are suckling for comfort which is fine, except that this pattern often exhausts and stresses the mom. The breast should not be used as a pacifier. Remember that these are suggestions, not written in stone. Every baby is different.