A picture would be helping a bit...outer capped cell is usually
honey, they leave the center open for queen to lay in.
Pollen is usually a sign that a queen is around. Too bad you only have one hive... If you had two packages installed you could compare. Center queen cells are usually supercedure cells, it seems the queen might still be around. I would check again and if absolutely no queen is around and eggs then a
a new queen would be in order, bees make queen cells allot,.. emergency cells encase they need it.

Here is a link that might be useful: Are They Supersedure or Swarm Cells?

I wonder if I can hop in here, too. I have two hives and I botched both installations to the point where I'm not the least bit certain I have queens in either.
I'm a little embarrassed to ask this, but when I inspected the top bar hive bars with hanging comb, the comb was covered with bees. I presume I am to brush those bees off the comb in order to inspect it? I am hoping to somehow discover some queen activity, but I could barely see the comb for the bees.

No problem... don't know, I don't run top bar hives. I can see when comb building takes place on one or a couple of bars you have tons of bees gathered tightly together an almost not possible to see brood.
I find the brush is the worst tool in bee keeping, it makes bees angry, I don't use it anymore, a feather would be better to gently move them. I would use a bit of smoke to make them move a little until you see comb. I know, top bar is getting popular lately for good reason's but it has it's drawback, [many] not something I like to start in the near future.