Do not limit feeding times. There are no rules how often or for how long a baby should nurse. Let the baby determine his own feeding schedule and things usually come right, if the baby is suckling and drinking at the breast and having at least 2-3 substantial yellow bowel movements each day. I can express only half an ounce of milk. This means nothing and should not influence you.
Most mothers have plenty of milk.
The problem usually is that the baby is not getting the milk that is there, either because he is latched on poorly, or the suckle is ineffective or both. These problems can often be fixed easily. The baby will take a bottle after feeding. This does not necessarily mean that the baby is still hungry. This is not a good test, as bottles may interfere with breastfeeding.