Since I don't believe in leaving help hanging - I'm back! :)
I think a multitude of things have added up to my issues. I (was) overdue on my chain maintenance. I did my clean and lube and some of the feel went away. I cleaned again, and a little more went away. There is no discernible lateral movement in the tire though, with it off the ground.
However, I am due for a new rear tire, and that was my project today. Videos and 2 hours later, I'm bumming a ride off my shop buddy to a shop here in town. For whatever reason, I just couldn't get that 2nd bead over the rimwall. Anyway -IN looking at the carrier bearing, I think I notice some play and grittiness in it. Not a lot, but it would certainly make me think this is the issue. The two wheel bearings feel perfect and fine; smooth with no gritting when I spin them with my finger.
So, I think it's the carrier bearing I've been feeling. I have all balls on standby, so I can get the set with my next check. I will probably just replace all three in the rear.
Thanks everyone so much for the guidance and support. :) You all are the best.