I called the septic pumping guy, and he told me that adding an aerator to *any* part of my system is completely crazy, even the dosing tank. He said that the dosing tank holds a few hundred gallons, and when the siphon runs, it pulls out 90 gallons from the very center, where it's clear liquid. According to him, solids should be able to settle out in every part of the system, including the dosing tank. Even though it's been less than three years since he last pumped out the system, I'm going to have him clean it out and start fresh, with no disruptive agitation.
As for adding more vent pipes, that would involve a backhoe tearing up ground in front of the house, and I'm not going to do that.