...lotsa questions there...

In general, it is not unusual to find great(er) availability closer to flight time (except of course at peak times)—by that time IM has a good idea of what they expect to sell and seat that go unsold become spoiled...

As for cancel/rebook, etc... Keep in mind that origin/destination and routing changes incur the change fee, simple date changes do not; and yes, you can only change the outbound or inbound leg of an award.