Unfortunately I'm aware of all of that from watching countless hours of This Old House and learning many lessons from Rich Trethewey about forced air systems. I have no doubt that our home's system could be better designed, as there are plenty of things about our home that could have been designed better to my untrained eye. Unfortunately - as with so many things - a true solution would be costly. So until we replace our furnace (probably within the next few years, TBH), I'll look for cures for the symptoms.

We've kept the circulating fan running 24/7 for a few years now and that definitely helps. But we do keep our bedroom doors closed at night so our son can get better sleep while he's still young. In the master bedroom we're fortunate to have a return vent on the primary stack. The rest of the top floor has a return in the hallway farthest away from our son's door. As I mentioned earlier, his room also has at least one too-few vents in it. The room is about 12'x12' with a single vent in the corner, which is also the farthest run in the entire house so it probably doesn't have much oomph to it either.