>a) How can you tell if your hive is getting too crowded?
They will be bearding if it's crowded and hot. Keep in mind, though, they will swarm without being crowded at all, just strong and the right time of year.
>B) Can crowding take place even if there is plenty of empty foundation in place for expansion in the hive?
Not crowding, but reproductive swarming can certainly take place with a pile of supers on.
>C) During the summer months, can you have too much empty foundation is place on a given hive?
Not on a STRONG hive. In a weak hive they may not be able to guard and take care of that much space.
>What I'm trying to understand is............ can I prevent swarming, just by ensuring that the bees have plenty of space for expansion?
No. Absolutely not. They don't swarm only because they are crowded. That is just one cause of swarming that usually takes place later in the year.http://www.bushfarms.com/beesswarmcontrol.htm
>Will I create another type of problem by having lots of empty foundation in the hive for the the bees to fill with either brood or honey? (Summer time only)
Not if the hive is strong. But it also won't stop them from swarming. It will, however keep them from running out of space which is ONE cause of swarming.
It is the goal of any strong hive with the resources to swarm during the prime swarm season in order to reproduce. To stop this requires intervention.