I decided to try a different approach. Following unclejed613's example, I thought it would be good to use a cross-coupled feedback scheme, because it allows me to adjust the gain using only one resistor. It took me awhile to get this correct. It also uses a complementary driver for feedback, which exploits the VBE multiplier. We had a thread about this some time ago, so some might be interested in this as an example. Transistor Q9 balances the output voltages. You'll notice a slight difference in in the differential outputs, which is due to the circuits marginal common mode rejection. However, I'm only interested in getting a decent differential signal, so I'm calling it quits at this point, working to improve the CM rejection isn't really worth it for this project.
I did't want to re-invent the opamp for this project, but every 'simpler' circuit didn't give acceptable results. I still think I need to use discreets to get the performance and ruggedness I want, however.